I feel isolated...my so called 'friends' have ditched me...what should I do now?

Considering that your "friends" just ditched you, they are not great friends. If they are your friends they would go to you directly and ask about the rumors that the girl spreads. They should not take her word for anything. Or you should confront them again or just call them. Gosh I am so sorry. Last year I had no friends really so I sat in the library and did my studies. This year was much better so hopefully your life will clear and brighten up. : )