Samaire Armstrong, co-star of new body-swapping teen rom-com 'It's a Boy Girl Thing', which premieres in the UK on 26 December, is like a sweet, effervescent pixie.  Despite having flown to London the day before and done a full round of media appearances, she still looks as fresh as the proverbial daisy.  She tells Entertainmentwise.com what she learned from playing Nell, about her fashion label � and whether she and co-star hunk Kevin Zegers really are an item . . .

Nell, says Armstrong, is a pleasure of a girl. "She is like Sandra Dee, but is lot less buttoned up, more open.  She reads 'Romeo and Juliet' in her bed and she has her cat and she has her eyes on the future of going to Yale. She's in love with her family and in love with her present moment."

At first, though, Armstrong really wasn't attracted to the body-swap concept.  It was the last thing she wanted to do.  So initially she turned the role down.

"I want to play a princess!" she says with a laugh. "I want to play Queen Elizabeth!  That's the type of role I want to play. But a boy in High School playing football is not what I want to do!"

But after producers Elton John and David Furnish, and director Nick Curran approached her, she eventually gave in and said yes � and she reckons she learned a lot from playing the role.  "When you act like a boy, you get to finally evolve into the girl you get to be because you've gotten the whole boy out of your system!"

Had the role also taught her anything about men? Armstrong grins. "Oh gosh - nothing I didn't already know!" she says, ticking the items off on her fingers. "Eat, sleep, girls, girls, girls, girls, sleep, football, girls, girls, girls, football!"

Armstrong and Zegers would rehearse their roles, she says, by playing the other character to give their co-star an idea of where to take it. This was made easier as she and Zegers had a relaxed relationship from the moment they met, and this translated to their on-screen portrayals of the characters.    Though their closeness didn't go unremarked on set!

"People were like, 'Do not have sex until after . . .!' Armstrong exclaims. 'What are you talking about?  No way!' They thought we had a relationship going. We would just blush because it was the last thing � No, no!"

Following 'It's a Boy Girl Thing', Armstrong is working on another movie 'The Staircase', based on the true story of a man who kills his wife.  She also has a role in 'Around June' a romance based in San Francisco, a movie which appealed to her love of colour.

"The first page was like 'The blue light, and the rain' and I went, 'Wow!'" Armstrong says with clear excitement.  "It takes place in the rain and they close their eyes and they have dreams and imagination in animation.  It's really beautiful." 

Although Armstrong never wanted to do anything other than act for as long as she can remember � as she says "It was like I came out of the womb like that!" - she is also a talented fashion designer with her own label, Nadu (Japanese for "becoming").  The line started almost by accident after she moved to LA and didn't have much money for clothes.  Needing an outfit for a red carpet event, she made one � and was promptly photographed by a reporter from Women's Wear Daily.  And Nadu was born!

But really, are she and Zegers together?  "No!" she says firmly, "NO!"

'It's A Boy Girl Things' is out On December 26.