Ah, good old jealousy. It's always jealousy when it comes to people who spread rumours :/ Shows how really insecure people can be.
I'm sorry you have to deal with such a person, Vishy-chan :( My first suggestion would be to talk to her about it and stand up for yourself. Show people that you're not that kind of person she's making you out to be, but you said you're a relatively quiet person so you probably don't want to go with that option. My other suggestion would be to acknowledge that rumours are being spread about you but don't show that you give a flying crap about them. She wants a reaction from you, she wants to see that you're upset by it. Even though they hurt, don't let it get to you because in the end, why waste your time on a pathetic girl that has nothing better to do with her sorry excuse of a life?
You're probably thinking, "that's easier said then done Invisible Hero", and you're right. It is hard to not let something that isn't true and is really upsetting not get to you, but keep your head held high Vishy-chan, remember that you're an awesome, smart, strong and an incredibly sweet person. So take care of yourself, immerse yourself in friends that really care about you (like Gama-chan, Ali-chan and I :P ) and the things that you love.
You could also talk to your parents and have them talk to the school, but sometimes that's not the greatest option as it can make things worse.
With your no friend situation at college though, do you have clubs that you could join (that interest you of course) or volunteer stuff? It's a good way to meet people :)