She is shallow and looks is everything to her.
Most Helpful Girl
If she keeps having "things" with other guys then she's likely not interested in you right now. If I had a great guy in front of me that I really like and feel attracted to then it doesn't make sense on any logical grounds that I'll try dating other guys nevermind sleeping with them.
I'm not sure if she'll come back but please keep in mind that she was willing to screw you over twice now by dating other people instead of giving you a go. At some point you need to ask yourself if it's worth it.
Most Helpful Guy
I don't know what shallow means, but if she's happy with that guy then she won't unless she has stronger feelings for you. If she's gone, then call her to make sure and just move on as friends. I really like this girl but she has a boyfriend so I didn't really try even though a lot of people thought we were dating lol. We're just friends and she is getting close to breaking up with him I don't know why though lol