Nothing meaningless about asking him to teach her, if she wants she can save him that much more effort on it after she's learned how.
She's not exactly limited to how many times she can make use of that knowledge after obtaining it.
@elfalas if its the surprise factor then yes its meaningless. or if its for the momentary tiredness. as he lack sleep past days. but she rather then lessen increased it. buy asking him to teach her.
I neED MOAR!
Seriously though this is some good shit, in the recent years more and more of this sort of stuff comes out, if only the rest of the world read this type of wholesome stuff.