FSU and the pd probably didn't take her seriously because she changed her story several times. The FSU and Tallahassee PD's do suck, but it still doesn't mean he raped her.
Also, they met at Potbelly's. The only people that go to Pot's are fraternities, sororities, athletes and girls looking to be picked up by said frat boys or athletes. I know that seems like a crass generalization, but it's true. I'd also find it very hard to believe the accuser didn't know who she was leaving the bar with.
Again, I have more issues with Winston's other crimes than I do with this.