"How old are you?"

So today I was talking to a girl and she asked how old I was. I am an older guy, I said something like old as hell how old are you? She said 21 and I said, "Oooh an older woman!" Here's the thing, it didn't sound like a shit test, it sounded like a genuine concern. My question is, if it is a genuine concern and a girl is weird about dating older men, is there anything you can do?