Hey there, I don't have any words of wisdom because I simply haven't been in your situation before (I'm 22, only had one boyfriend before).

The one thing I CAN think of to ask is if you've talked to her about how you feel? Although I don't think you have a right to insist she stay, I do think you have a right to express your feelings on the matter. Good communication is necessary in any good relationship.

Take care of yourself, hope writing helps you *it does help me*