I have a crush on a girl with a boyfriend who treats her like ****.lol?

OK...im 18 and i have a crush on this girl who is possibly the girl i can see myself being with. I honestly wanna change my ways, stop messin around, and settle with one..and shes it. When i picture the perfect girl..theres her reflection. ok thats the good stuff...the bad is..she has a boyfriend. now usually i dont ask for advice cuz im the one who's always giving it, but i wanna kno...what can i do to help her realize her man isnt the one? he treats her like ****, cheats on her, talks to a series of other women, and plays her right to her face. But this girl likes me alot and even told me she needs a guy like me in her life. i figure 1: She wants me to make a move (but im no home wrecker) 2. She's playing games or 3. She's scared of leaving him...but plz yahoo ppl...what should i do!!!