Matty, in all honesty, one of the reasons she is keeping you at arms length is because she knows she can. She got you. She knows she got you. She can get whatever she wants from you, whenever she wants. Its not malicious, its likely not even a conscious act on her part. But you're her emotional support while she ready's herself to meet the next person she falls for.
And I am not going to mince words with you Matty - if you continue doting over her, you WILL see her fall for someone else. Its not a question of if, its a question of when. And it will absolutely, positively crush you, doubly so if you keep allowing yourself to emotionally invest in the potential fantasy of 'someday'.
From similar stories from my past, and from friends & colleagues who have gone through similar, a very interesting thing happened once I pulled away from a girl that wanted to remain 'just friends' or emotional support, that I decided to pull away from because my intentions were purely romantic in nature. Once they realized I was no longer an option, they came CHASING after me. It's like that sudden realization that you're no longer a romantic option made them realize 'oh shit, this person is gone? I gotta get them back'.
Mind you, I wasn't being manipulative. Like you, in my HS days, I had a girl that I was enamored with that had just gotten out of a relationship, and just needed support. And I saw her fall for someone else, even though I was always there for her, hoping she'd turn to me someday. After that, I never allowed such a situation to happen again. A year after HS, a girl I had recently met tried to pull the same thing on me. Once I pulled away, she came chasing after me & got super clingy, to the point where I no longer wanted to be with her. I wasn't intentionally being manipulative; I wasn't pulling away hoping to win her over. I pulled away because its just the better move for everyone involved.
I'm not saying pulling away will win her over for you. Instead, what i'm saying is, pulling away from her will free you from caring about whether or not she ever will come around, and instead, will (hopefully) put you in the path of meeting someone that will wholly reciprocate your romantic interest. And let me tell you something - college is probably the very last mass social environment you will find yourself in, where meeting new people occurs on a daily basis. Most of us here who are past our college days are supplementing that social exposure with online dating. Do not throw away precious time that you have in such a fantastic setting to meet & have wonderful experiences with new people over someone who doesn't share the same feelings you do.