Friends and boys

I'm so glad I'm not into boys, being leisban might limit the dating pool a little but in trade off I get to love some extraordinarly beautiful, intelligent, respectful, amazing women. Well, anyway my straight female friend from high school is doing some diastrous shit to herself involving not one but two things with penises. (I refer to them that way because both men make my skin crawl not because I'm man hating lesbian who thinks men keep women down) Well, anyway my friend is cheating on her new boyfriend with her old boyfriend. The old boyfriend temporarily destroyed her life as in he choose to be kind of guy who shared every private thing about her on the internet, and she's choosing to hurt the 'better' guy by letting her old boy friend back into her life to be able to learn more private stuff about her. Why may I ask do humans feel the need to hurt themselves on the path to find Mr/ Mrs. Right?