Faith needed someone to understand her. She turned "evil" because she felt no one really understood, cared and loved her. She started seeing Angel as that person, who might care for her. So yeah, I believe he would have, not changed, but make her see the right path again. The path she got lost in. He knows how she feels, because they're very similar. And Faith noticed that. That's why Angel was the one to bring her back. Unlike Xander, who believed he and Faith had a connection. They didn't, and it failed. Buffy tried too, but she started giving up on her, because she tried to help her, but all she got from her was a spit in her face by Faith. Faith did think Buffy was the one who would bring her bright future, bright life (as much as bright future and life as a Slayer can have). But Buffy didn't really understand her, even though she was a Slayer as well. And the reason was that Buffy lived a different life. She had friends, family, boyfriend.... They weren't really walking in the same path, the same world. That's why Angel was the person who would have brought her back to being "good".