How to throw the bad guy out???

Well..i found this girl on the net and we became good friends chattin regularly and quite close too....soon i was impressed by her and fell in love with her..i proposed to her on the net but she refused but she was talkin to me as she did before and still considered me close to her...after our exams were over she invited me to her home and we became really close...when things were goin right 4 us..suddenly one of my enemies at skool(who once said bad things abt her) showed up at her home and started actin like a good friend to her...now she is not believin my words abt him and says he's good too...but it's clear to me he is actin...she started considerin him like me and sometimes more than me too...how can i make her understand my feelings and keep her away from him????