I think what Faith was attracted to in Buffy was the power and the popularity. Those were two things that Faith seems to have always wanted, and yet was always denied.
She did have power, as a Slayer, but she was always overshadowed by Buffy. Buffy was, and is, THE Slayer. Faith was just secondary.
Faith is attracted to people whom she views as tough, strong and powerful. At the same time, she also wants a normal life. So while she may be eager to dominate those who are above her, because she hates being below, and it comes across sexually (I think that line between sex and domination and aggression is very blurry when it comes to Faith), she also would not swing toward women. That much, I believe is evidenced by her comment concerning Willow... it was said in an almost condescending way. Not that she herself looks down on Willow, but that she could never do what Willow did.
Faith can be seen as many things while not being them. She can be seen as heartless and evil, but I really do not believe that she is. As evidenced in Angel. There's the saying, don't judge a book by its cover... don't judge Faith by how she comes across. She can be extremely brutal and honest, but she's got many layers there hiding the true Faith, and they only really started peeling after she and Angel had a long talk together.
