I'll weigh in. I'm going to assume your financial goals are different hence why your apprehension to marriage. I totally respect that. Maybe lower the rent amount by $50 so she feels like she wins. But I would set aside her rent money so god forbid you do breakup you can give some of it back for a security deposit somewhere else so she doesn't stay in your place.

I definitely agree this is more of a relationship issue since she's saving money over the apartment you shared. My guess is that she wants to get married and is hoping this will force your hand.

I think the arrangement you suggested is fair. My buddy had the arrangement that she suggested with his girlfriend. And they broke up. There were some other problems with their relationship obviously but in the end it wasn't worth the hassle to him.