Dating is a big step in life, especially to women who are looking for a potential future husband. So everyone has the right to be at least a little picky when choosing a partner, it's not superficial or racist, etc. Whether they end up single or in a long loving relationship is on them.
I do think it would be better for that White girl to keep that "I don't date Black guys comment" to herself in order to avoid drama and/or being unfairly attacked by Blacks, unless she was literally asked, "Would you ever date a Black guy?" In that case, she had to answer, and it's the asker's own fault if he didn't get the answer he wanted. I'm straight guy not physically attracted to Black women, but I never addmit this in public, cuz I don't want that drama.
Besides, Black people always call White women, "plain, basic, Becky, pasty, flat, etc." and no one bats an eye. Yet if someone says the tiniest negative thing about Black Afrocentric people/features, they get crucified. Double Standards.