I don't understand why you don't just tell her how you feel about her and ask how she feels about going out with you.

She obviously likes you. Women do NOT hug and kiss (however innocently) men that they don't like.

Oh, and I think the fact that she has a boyfriend is irrelevant. In my book, you have a right to ask her if she would like to CHANGE boyfriends (to you). She won't be offended, but rather flattered. (If the boyfriend were a friend of yours, that would be a whole different matter.)