I guess it's some kind of closure, and it's not as bad as I thought it was.
It's not because she lost attraction... we had sex just before ending the relationship (No attraction = no sex)
It's simply because she is completely overwhelmed by her work and just needs time and space to work on it. Being in a relationship as well as having to put a lot of effort into her studies/exams was just way, way too much.
I'll just give her the space she needs until I know her exams are over, and I'll probably contact her then when her head is cleared up.