What should i do?

So lets set story chinese bisexual girl talks to me on imvu -> she then adds me on msn. KNOWN THIS GIRL FOR 3 YEARS [SHE'S 15 AND IM 17]
Emails me about how sexy i am and that she is in love with me and wants to have sex with me.

She then tells me she has sexually abused dogs and that she is the "local bike" [sexually active]
Messages wont stop.

She then told me that shes a virgin and wants me to lose her virginity [im a virgin anyway]

Then yesterday she says "Can I see a photo of your step bro?"
I say no.
Then she said "I know what you, me and your step bro have a threesome"
Yeah my bros hot but still I would never do that. [HE'S 30]

I do not know what to do anymore as its getting out of hand. She wont give up!! She tells me she knows where my house is. I do not want to get a reputation. Im not a lesbian. Yes she is a nice girl but i dont know what to think and if i did i would probably catch something also would not want to be accused of being a perv or anything.