It means she will appreciate you more and less likely to cheat
Most Helpful Girl
I think it depends on the person. Everyone seemed to agree that I was better looking than my ex boyfriend (including himself) and yet... He cheated on me.
During the time I was with him I was very loyal to him - I'd stopped calling one of my guy friends on Skype, stopped trying to get previous guys I liked to like me, when I found out one of my past crushes liked me I kept away from him and didn't do anything and even rejected someone. I don't want a reward for that because I know being loyal to someone when you're in a relationship is something that you SHOULD do.
However, despite apparently being more attractive than him, I was more loyal than he was and he obviously did not appreciate me enough.2
Most Helpful Guy
When does that ever mean she is less likely to cheat?
You are basically saying that prettier girls are dishonest and immoral, while ugly girls are honest and loyal. While prettier girls are going to get more male attention, it is still up to her whether to cheat or not. If you've watched Jerry Springer, you'll see that even the ugliest of the ugly girls are just as capable of cheating as anyone else.
Cheating is not due to how attractive a person is.
Cheating is the result of either an unhappy relationship where the emotional bonds are not being met. Or the result of a self-centered POS who thinks only for their own benefit.1