You sound like a bit of a stalker! Surely it's not healthy to document every step of your interactions with this girl? "if you want to go just tell me" sounds like she was subtley telling you to push off. Seriously, you're from the same college - you'd have found something to talk about if she was inclined to. If you've withdrawn from uni and are planning to study again, I suggest you chose somewhere that you like for proper reasons, rather than because you overheard that some girl you barely know might be going as well!
You know what, you're juts gonna have to bite the bullet. Ask her out! If she says no, it doesn't sound like you see her that much so it's no big deal, and you can move on. Sound like you have a chance, i'd go for it.
I think its in your best interest to just forget about her. She's probably sick of being stalked too, maybe thats why she doesn't make effort with you.