[belladoggy]

If he cheated on her, chances are he will cheat on you. If she's as a good a friend as you're saying she is, then she really does want you to avoid getting hurt. She knows from experience that this guy isn't the best at handling relationships, so I'd say she's qualified to tell you to turn him down. If he hadn't cheated on her, I'd be more likely to think it was just jealousy, but the thing about cheaters is that they have a reputation of being repeat offenders, even if they say they will "change."