You don't think I can guess just from your mental voice, huh? Well let's give it a shot.

[He may be way off, but that's not the point. The idea is to always guess around the same age range. If it's too low but not insultingly low, she might be flattered. Same thing with it being too high.]

I'm going to say... Twenty-five? Tell me I'm close.

[Right about there should be the sweet spot.]