This is a generational thing. It absolutely is a real relationship to the people involved. There are hundreds of people who will read your comment in relationships like this, so, prepare for that.

That said, I am extremely wary of living with people I'm not related to after being burned by people I did know in person. Your concern both for your space & your gf's daughter are valid. How you came at the situation is not great, but I think if you use the points you've fleshed out in discussing it here & keep your cool, your family will see your side.

It would be a nice idea that would buy you some goodwill if you offered to help look for apartments & collect job listings for the boyfriend.