You know society has failed when...

There are some people who are just naturally creepy. The kind of people, no matter what facial expression they make, looks like they want to rape you. But in your case OP maybe age has something to do with it. Are you significantly older than she is, and/or was she younger than 18?

While I hate to be the person who extrapolates on FML situations without having any info beyond what the OP provides, something really is not adding up here. Were you stalking her or something before this? Even if we just assume the girl was nuts, that reaction does not make sense unless there's another part of this we're missing. This story has a severe "jilted man edits what happened in his head because feelings are still raw and clearly she is just crazy for rejecting me" vibe.

Only in USA do they sue people for romantic feelings.

Politeness has become so rare that some people mistaken it for flirtation

I think she likes you

I feel like there's more to it than this. Maybe you said or did something inappropriate, like unwanted physical contact (anywhere, at all) or a lewd comment that could be construed as harassment or intimidating. I have to ask: do you actually know her or is she just a girl who is in one of your lectures/a girl you see walking around sometimes? I've read a few FMLs recently about people 'falling in love' with someone they see around campus but have never spoken to, and it's pretty creepy. If that's the case, I really wouldn't blame her for feeling intimidated or upset.

She probably thinks you're stalking her

You do sound like a stalker, I would have done the same

Bitches be crazy.