I personally don't remember it was ever revealed. But this movie reviewer complained that Aaron Paul's character was dumb because the audience could figure out Claire's real name before his character did. Really?
Why would his character ask her who she is at the end if he already knew? Furthermore, were ANY of her aliases foreshadowed? Or is this reviewer full of it?
She reveals one name near the end but she also writes one name on her arm when they are painting - those are not the same names (the one where they have been painting seems like the real one to me and that was Sarah). Kim was the last name she mentions in the movie and even though they should be level at that point it seems like she got less invested in that which probably would make that her first "new" name or something along those lines.
This is excluding any subplot which I did not care for to properly follow other than to notice the shifts in twilight, morning, day etc depending on where the characters are in the plotline.
[EDIT] Sentence structure. [EDIT 2] Spelling.
Ignorance is only a bliss if you haven't reached awareness. My imdb posts are getting altered.