How long can girls date anyone they want?

There's a girl I know that I work with, who is extremely physically attractive, she's 22 and seems that she can date any guy she wants. When I met her she seemed cool and the conversations were pretty general as far as subject, but I found out a little bit later that she was making fun of me behind my back and whatever, so I don't talk to her anymore. I think she's the type of person that feels better about herself if she puts others down. She was also dating some guy for a couple years, but during the whole time was cheating on him, she flirts with every guy she comes in contact with, uses people, and pretty much treats people like crap. Anyways, my question is, it seems that she can go around and do whatever she wants with no consequences, and I personally think it's only because of her physical appearance. It's kinda upsetting to me, because for me it's a struggle to even get anyone to talk to me and I always treat people well, and I never did anything to provoke her. I've heard that girls that are really attractive don't last to long or may become really unattractive, and the average girl will have an up on her in a couple years, is that true? Why does it seem that every really attractive girl I come in contact with has a horrible personality? What happens to people like this?How long can girls date anyone they want?
It all depends on how you carry yourself. You can look average, and have an amazing personality that draws people to you, and you can get everybody. Or you can be very attractive on the outside, but a pure b***h on the inside, and no one will want to be with you (with the exception of guys that only want one thing). My advice is to just be yourself. I have many very pretty friends with beautiful personalities. But for the ones without beautiful personalities, what goes around eventually comes around.