@Eliusa,
Lordy you can be so rude Eliusa, such a temper.
Simple. If that was my daughter, I'd laugh (at him) and tell her, he's in love with someone else, don't be his little bunny, that someone he can call upon every time he's down and missing (the other woman)... followed by "You're better than that"...
Give her the confidence she needs to feel strong about herself obviously she doesn't.
Saying WTF? Isn't going to help her in any way shape and form and your old enough to know how to handle this, don't try to be her age and immature, in your converse.