How do you get a sim from university to move into your normal world

This has driven me mad today. 3 times I've invited the lovely nerd Richard to visit his girlfriend who's now back in Aurora Skies, he's turned up on 3 seperate days, they date hang out, have a meal etc but no matter what she does the option to ask to move in never appears.
The relationship is as high as it can be, they can make out even woohoo but the move in question is never there. She can't seem to propose marriage either, so it looks like he might get away :(