She's doing the thing that women always do: she is pretending that her perspective is the only possible/rational/moral perspective.
She likes men her own age, so therefore liking people your own age = moral. And if men don't like women their age (read: her age) then men are immoral. It is literally that simple.
You could easily turn this around on her (as if anyone in society would care) by saying, "I don't care how much money a girl makes, so therefore it's immoral for you to care how much money I make. I don't care how tall you are, so therefore it's immoral for you to care how tall I am" - nobody would buy that logic though, because everyone acknowledges that women have the right to have whatever preferences they want.