"That was a nice birthday present. I mean, how cool is that?" she asks and it's hard not to agree that it is indeed a special moment. But then, since she appeared in Steven Soderbergh's award winning Traffic, playing Michael Douglas's drug addicted daughter, almost two years ago, life has been particularly good and Ms Christensen would be the first one to tell you how much she appreciates it.
"Yes, I definitely have a different life, before and after Traffic," she says. "I really couldn't have asked for a better movie to get a good foot hold. It was an incredible role for me, an incredible script, director and a great cast and it was about a subject that I'm really passionate about and interested in, as subject that is relevant to any part of the world. So it was just an amazing experience, I had a blast doing it. "
But even before Traffic - in fact ever since she was 12 years old - Erika has been working hard and building a reputation as one of her generation's most talented young actors.
Born in Seattle the eldest of three children (she has younger brothers, twins, aged 16) her family moved to Los Angeles when she was just four and she discovered a love of performing after her mother, Kathy, persuaded her to join a children's theatre group to give her some after school distractions.
"When I was 11 my Mum found this group of kids who just did performances around LA, they sang songs and danced and she thought it might be fun for me so I went ahead and joined this group, got over my stage fright and performed around LA for a year or so and fell in love with being on stage, that rush you get from connecting with the people in the audience," she recalls.
"And then at about 12 I just knew, something clicked, and I knew I wanted to be an actor and my parents, to their credit, granted this 12 year old girl a chance to give it a try. They helped me find an agent and a manger and I immediately started working, doing commercials, and they realised I really could be an actor and we've never looked back. "
By 13, she had won a starring role in Disney's Leave It To Beaver, and over the next few years notched up an impressive string of appearances in top US television shows like Frasier, The Practice and Third Rock From The Sun.
Since Traffic, she has hardly stopped. There's the yet to be released Home Room, a drama centred on a High School shooting, the much anticipated comedy, The Banger Sisters in which she stars alongside Goldie Hawn, Geoffrey Rush and Susan Sarandon (playing the latter's daughter) and of course, the thriller Swimfan
When we speak, she is back at work on another drama, Perfect Score, filming in Vancouver.
Directed by Australian John Polson - who as an actor has starred alongside Russell Crowe in The Sum of Us and with Tom Cruise in Mission Impossible 2 - Swimfan is a gripping thriller about an obsessive stalker.
Jesse Bradford plays Ben, a reformed bad boy who finds purpose to his life after discovering his talent as a swimmer. After earlier run ins with the law, he's now a grade A student, a top athlete with Olympic potential and happily settled with a girl he loves, Amy (Shiri Appleby).
Then he meets the new girl at school Madison (Christensen), a beautiful and mysterious newcomer who is obviously attracted to the most popular boy in town. They meet, seemingly by chance, and Ben tell her that he has a girlfriend. But Madison is not easily deterred and they meet again, seemingly by chance.
Finally, her persistence pays off when she seduces him in a one night stand. But guilt ridden Ben makes it clear that he wants friendship and nothing more. Madison has other ideas and begins to stalk him, gradually worming her way into every area of his life - she visits his mother, becomes friends with his girlfriend and even dates his best pal in a bid to make him jealous. And then Madison's unwanted attentions become far more sinister.
Madison is not exactly the most endearing role you will ever play. ..
(laughs) She is one of those on an actor's wish list, you know you want to play someone who is just over the edge and I had a blast doing it. I mostly have fun wherever I go and whatever I do and I really did have great fun playing her. But you're right, she's not exactly the most endearing role, but these things balance out. In The Perfect Score, which I'm shooting now, my character is a much nicer person.
How would you describe Swimfan?
I think it's a great thriller. I'm not too sure that people should put labels on it, like 'teen movie' I just think it's a good film. I'm very, very pleased with it. A lot of adults have been telling me that they really liked it or wanted to see it because it looks like a good thriller and it is, it's intelligent and it's not gratuitously violent, it's a good scary film. John (Polson) is a great director and that's one of the reasons I wanted to do it. I knew it would be great working with John and it was.
And it's good to play bad. ..
Yeah it is. But she's not one dimensional. I mean, she has vulnerabilities and as we find out more about her you realise that all is not quite as it should be (laughs). But you can play a villain in different ways. It's better, I think, to play her mixed with a little vulnerability.
There's a very sexy love scene in the film. Was that your first?
It wasn't the first. It was certainly the trickiest or the scariest or the most passionate (laughs).
Difficult to get those things right, I would assume, especially when you happen to be in a swimming pool. .. ?
Not as much as I'd expected, let me put it that way. It went swimmingly (laughs) we just kept the atmosphere light and joked around and John Polson was in his bathing suit too, the water was warm and it ended up just being another day at work. .
But I hear you persuaded the crew to help ease the atmosphere. ..
(laughs). I got the sound guy to play Marvin Gaye's Let's Get It On. It was very funny and Jesse was cracking up. He had no idea it was going to happen. That helped ease the tension, I think.
Things are going very well for you. ..
Yes, they are.
Did you realise that Traffic would be such an important film for you?
I had a clue, yeah (laughs) I practically hyper ventilated when I got the job.
And since then you've filmed Swimfan and The Banger Sisters. ..
Yeah, The Banger Sisters, that's a comedy and it's coming out next month too. It was a blast. Oh my God, you can imagine the experience of watching these women, Goldie (Hawn) and Susan (Sarandon) are these legends, just watching them work was really great for me, they set such a good example and they had a great balance between being a real pro, being prepared and having fun and having a great sense of humour.
Have you seen it yet?
I have and it's a lot of fun. It's a great movie and been marketed as a chick flick, which I can understand, but I have younger brothers, twins, and they are 16 and they loved it. I think it will hit a pretty wide audience. ..
Where are you from?
I was born in Seattle and grew up in the suburbs of LA. I was four when I left Seattle.
What do Mum and Dad do?
Now, they both work for my production company.
Were they in the business before?
No, not at all. My mother, Kathy, was a construction manager and my father, Steve, worked in insurance.
What prompted the move to LA?
If you ask my mother she will always say it was the weather, we get spoiled there, it's beautiful. But really it was a combination of many things including the climate, my Dad had a job opportunity and it was kind of a hustling, bustling community and my parents wanted to make sure we had a nice social upbringing.
I presume with a name like Christensen there is some Scandinavian in your heritage?
Yes sir. Great grandmother. She just passed away a couple of years ago. I have Danish, Norwegian, Irish, what else? Welsh and a tiny bit of Swedish I think, just a dash.
Have you been to any of those places?
I haven't yet, but listen I really want to and I will.
You acted all through your teen years. How did that work with your schooling?
I was in a private school when I started and I was never there. When I started working because I was either working or leaving in the middle of the day for auditions so I did stop going to private school and started doing home schooling and then it was a combination of that and on set tutoring.
Did you feel that you missed out on the High School life?
I think I gained in other ways. I have absolutely no regrets because I knew so strongly that this was what I wanted to be doing. And I'm so glad that I was able to. I mean, my life would have been so different if I had only started acting a year ago when I was 18 but as it turned out I did home schooling, I got my diploma at 16, I made Traffic at 17, so my life is really is much more on the course I wanted it to be on - acting.
After Traffic, you must be recognised a lot. How has that been?
It's definitely been fun. I mean I knew what I was getting myself into, I knew what being a successful actor implied and I really wanted to be a successful actor so it wasn't entirely a surprise although I can tell you it has been slightly overwhelming at times. And it reminds me to kind of set a good example, which is my instinct anyway, but it's an interesting way to remind me of my morals, to know that people know who I am.
Do you find that your friends are mostly actors or outside the business?
Both. I have a lot of friends that I've met through work and a lot that I've met through mutual friends that are actors, it all goes around in a circle. But then I have a lot of friends from the private school I went to when I was 12, I still know them, I go to their school plays and their proms. I'm still very much a part of that. I've got friends from church, the school that my younger brothers go to, I meet people everywhere. It's great.
Are you a church going family?
Yeah, we're Scientologists.
Has that been from an early age?
Yeah, I started studying when I was I guess around 12. 12 was a big year for me, I grew up a little bit that year. My brothers have been starting to study in the last couple of years and my parents both became Scientologists when they were around 20 years old. It's really a wonderful thing that means a lot to me.
Are your brothers showing any signs of following big sister into acting?
They are but in an interesting way. Dane and Brando did a pilot last year and they are wonderful actors, blew me away, but they are more interested in being behind the camera. They've made some short films of their friends and I think they are extremely talented.
You have your own production company?
It's called Endless Entertainment and we haven't produced anything yet, but we have a couple of stories in the works. We cooked that name up, me and my parents.
It must be nice to have your parents so closely involved in your career?
Absolutely, they certainly have my best interests at heart. My Dad helps me to read all the scripts that come in and keeps track of all the finances and my Mom does everything from taking care of the scheduling to making sure everybody is on the same page, my agent and my manager and my publicist and me and they just really help me to keep myself organised and keep myself rolling. It's unbelievable how much work has to go into it. But these are the good problems to have, the problems I've always wanted, trying to figure out when to sleep in the midst of flying to a press junket and working and all that kind of thing. .. .. (laughs)
Do you look very much to the future?
You know, I do. I take things on a day to day basis when it gets really hectic. But I do think long term and I'm looking forward to the next couple of years when I do start producing my own films with my production company and playing some characters that are older and that's really exciting to me. And I'm really looking forward to just continuing to be able to do more, work with more people that I respect.