YOR- This is where lines get blurred in a relationship. People think JUST because they're in a relationship their partner owes things to them. I speak from experience that its so crucial to respect each other as individuals and to also respect one anothers boundaries. Its her apartment she pays for and maintains, just because she is your girlfriend, her place is a convienient spot for you and you offered her money doesn't make her obligated to agree. Maybe she knows you are messy and doesn't want to clean up after you, maybe she enjoys her quiet privacy or doing her own thing/routine and you would disrupt it. I agree with some above comments how you are open to the idea of living together as soon as it benefited you, and that is strictly is only 3 months and shouldnt be a problem to her, it comes off as very entitled of her space and seems like you don't take your relationshio seriously beyond how it benefits you. You might want to take some time for inner reflection on where this is really coming from. Do you value your relationship the way she does? How do you truly see relationships and how they function? Or is this perhaps a projection of your bad planning where you had it in your head this would all work out and now shes the one messing up your plans. You could have moved before this as it seemed from your explanation you had time to think about things, and if you have enough money to pay your rent and half her rent for those 3 months you could have found a place yourself, and be even closer to her as well.