Why does it hurt though? It's just part of life. Everyone rubs someone up the wrong way for absolutely no reason sometimes. You've just found someone who can't stand you, that's their problem, not yours.
You've probably not even done anything to annoy her. She may just have taken an irrational dislike to you. There was a guy I used to work with, let's call him Steve (for that was his name). I absolutely loathed Steve. I couldn't tell you why, everyone else seemed to like him, on paper he seemed like a nice guy. There was just something about him that I found really unpleasant to be around, made my skin crawl. I never let it show, at least I hope not. I hope I hid it better than your college person did at least.
And then one day I'm in the pub after work with a bunch of other colleagues, and we bump into my Dad. He says Hello, I introduce my colleagues, and we have a short conversation. My Dad buggers off one of my colleagues pipes up "You know, if I didn't know he was your Dad, I'd have said he was Steve's"
And suddenly it all fell into place. Me and my Dad have had a somewhat turbulent relationship over the years. In short, he's a womanising twat, who has a desperate need for everyone to like him, especially women. He needs to be the center of the room, often at the expense of everyone else around him.
Steve was not like that, not really, but he was enough like that, and weirdly shared a superficial resemblance to my Dad, that something in my brain went "Nope, I've already got that bellend in my life, don't need another version of him."
I'd like to say that having had this realisation, I became firm friends with Steve. But no, I loathed him until the day I left the company. But at least I loathed him knowing that that loathing was more about me than about Steve.
Who knows why your course-mate hates you @DeflatedInDerby . She may not even know why. You may have done something grossly offensive to her and not realised, but equally, you may just be her Steve.
All you can do is accept that you can't be liked by everyone, and get on with your life.