Molly is being quite selfish, here. She insists on Mike moving in with her and she's hardly letting him keep any of his stuff or put it anywhere in her house. They should wait until they're married before living together.
I actually do agree with Peggy's idea, don't live together until you have rings on your fingers and rice in your hair. That's actually the way my girlfriend and I think it should be done because our parents did it the same way. But this is only my opinion, I'm not telling anybody how they should live their lives.