He did that at 13 or younger!? She would take that...not as badly as I would. lol. Especially since she fell in love with her much older husband at 13. I figure she was probably 16 before they had sex. >_> And definitely because she prompted it. ...Maybe 15.
She would probably initially be a little surprised by that, but then it would probably make too much sense, like, ah ha! No wonder you're...like you are.
And she'd proceed to explain with less weirdness because doing it once still leaves plenty unexplained and it's different with girls and she'd probably feel less awkward at that point. She'd also hope he'd ask questions if he wanted too.