Oddly enough something similar happened to me on St. Patty's day. I had been crushing on this girl for who knows how long, she is the super flirty type always sitting on my lap, holding hands we kissed on more than one occasion. Honestly it sucks when a girl is that flirty, all the normal signals get completely confused and there is no way to tell if she is actually interested. Unfortunately for me after already having a rough night I got sick of her being flirty, told her I liked her and got rejected. After this happened I called her a cock tease and told her off, which actually made me feel better but I haven't talked to her since, and probably won't anytime soon.
The whole lets just be friends speech always sucks.
As far as meeting people goes, I say do whatever you can to meet as many people as possible. You'll never have more opportunities than in college to meet people, a fact I can attest to having been away from school for two years now, my social life has seriously stagnated. More people randomly come into your life in college than anywhere else. As for meeting different kinds of people, it might help joining a club or something. Have you throught about getting people together from your classes to meet in the library to study? I didn't start doing this until I was a junior when harder classes pretty much make it necessary, but I actually got to know a lot of different people I wouldn't have otherwise met. Nearly everyone is receptive to meeting in the library to study for an hour or two on a weeknight.