Maybe, but it doesn't make it any less of a mature thing to know now. When you learned it isn't as important as the fact that you did learn it.

[Again, not the reaction she was expecting, and this line of questioning is starting to feel a little personal. Not enough that she'll stop, mind you, but she resolves to be a little more careful about it.] How long ago were you together? She seemed pretty comfortable trying to find you a date, so I'm guessing this isn't a "we broke up six months ago" deal.