why do people have to spread rumors about me when things are going so good

... I mean I finally got the girl I want

......And then BOOM...This girl is saying that we slept together and we didn't and eveyone is believing her! Ahh....It makes me so freaking mad...she is one of my best friends and yes I did turn her down but for her to tell a lie like that and then let our friends treat me like a low life dog for not admitting to it

.....why would a friend do that to you.....espeacially when everything is going so freaking great!!! I hate it!!! so can you tell me? why a person would be so mean and vile?