What was Lena's part in the story?

I could be wrong, but I think that the film would have played out in the exact same way if Lena wasn't a part of it. Hans would still have gotten caught, he would still have been in the stadium, he would still have been sent to the camp. Lena had no part in this. Also, Lena didn't come up with an escape plan, she had to rely on Hans for that.

To me it looks like her only contribution in the film was to be the eyes of the audience. Like a fresh to gaze to examine life in the camp. I read somewhere that Emma Watson wanted to play the part of Lena because in this film the female character rescues the male. But the way I saw it, she didn't rescue Hans. If anything, she only got herself into more and more trouble and Hans succesfully got her out of it.

Again, I might be dead wrong in all of this. What do you think?