The game should really make an exception with family members' or boyfriends/girlfriends' homes. I wanted my sim to visit her father for new years eve, but I really had to add her to the household for two sim days so she could actually sleep there. Or when another sim visited her boyfriend, I had to buy the always welcome trait so she could actually stay the night there.
It would be nice if there was an option to ask another sim to stay the night at their house, as it's also possible the other way around.