Hi LiJ
Your third sentence is the most natural. Your first sentence is OK, but it seems somewhat incomplete without any context telling us the reason why she is just now becoming stuck-up.
Your second sentence sounds odd to me. Using the word 'for', I might say something like this:
She's getting far too stuck up for her own good.
EDIT:
Oops, I see there have been two other posts in the meantime.
![Surprise [:O]](/emoticons/emotion-3.gif)