Nah, if they were living together and if she was dating him, you can be sure she either would have convinced him to make it clear and would brag about it on social media like any girl her age would or he would have told her to tone it down and she wouldn’t be posting all those pictures and videos. The second option would me more likely. But in no case, his girlfriend would be a 24 years old throwing college parties in his garden while he’s away.