how can I deal with a girl obsessed with me?

cw: suggestive mentions.

okay so, I'm running out of ideas. I'm a uni student and last semester my friends went to a different class so I ended up alone and had no one to be with. A girl that sometimes interacted with my friend group started sitting with me and at first she looked okay so I didn't mind it, I was cordial to her out of basic human kindness but this semester it looks like things weren't like I thought. I thought she was weird because last semester she had this thing where she liked invading my personal space, tried to peek into personal stuff of mine and things like that. She then started doing whatever for me, like very mundane tasks and while I know it's a kind action she took it a little too serious and tried doing everything for me. 

I had friends that were in the same class with her this semester and they have told me that she talks about me saying that she's close to me, we talk everyday, if we ever have a class trip I'll always go with her, she's gonna change classes next semester to be with me again and even in one of their conversations she said that if she was a man, she'd have her w4y with me. Three times. It's really starting to creep me out. And on top of that she doesn't respect the fact that I don't enjoy nor let people touch me which is just overwhelming because I'm starting to get used to togetherness with people I do trust and she somehow thinks she can do what she wants? It's so annoying. 

Now I know that the best course of action is just not engage with her, and I already do that, I've been ignoring her but she doesn't seem to understand that I don't want her around. I don't enable any of those behaviors because the nicest thing I've said once is that she "saved" me from a lil trouble I had last semester and it seems that was enough to make her get weird. I really thought people lied when they said there is some people that get obsessed if u show even an ounce of kindness but I guess this is karma for doubting that. 

I'd like any ideas from someone who has dealt with this and the perspective of someone who may have those behaviors because then I could at least try to understand what is making her act this way.