How would a guy use a girl for an ego-boost?

[MrsTurkleton]

He does all of the above.
He will give her enough attention to keep her around, not because he cares for her, but because she cares for him.
If he senses she is pulling away, he will say and do all the right things. She'll think he's making an effort, but he just doesn't want to lose the attention he gets from her, or the high opinion she holds him in.
As soon as someone new gives him the same kind of validation, he'll drop her.

[Tututwerl09]

He uses her because of her looks apparently. And also because she knows she like him. So I'm sure she's giving him attention making him feel really good.