simon_says wrote:
Well, if you want to steal her you just have to befriend her and wait for the right moment to step in. It certainly can work, it's just not the most likely outcome. It's not cheating if she just openly switches partners because she's not happy and you seem like a better partner.
Then she'd be rebounding, which means the relationship is doomed from the start. Unless he's willing to pull the tricks that boys pull when they're pretending to be a girl's friend (eg. saying things like "if I was your boyfriend...", flirting, finding excuses to be closer, giving her "friend" gifts, etc), then he runs the risk of only being considered a friend. And, if he's going to pull the tricks, then he's being underhanded and sleazy, which I'm sure is something the OP does not want to be.
Not only is this unlikely to be successful, like you said, but it's also a colossal amount of work and I'm just not sure any person is worth it.