Need more money from a friend

Bit of a long story. But need advice. I'm looking to rent out my one bedroom apartment in NYC to someone. There's not enough closet space for myself. I hate that it's on the first floor with absolutely no view at all. Super Great neighborhood. Beautiful area but it's very outdated. Parking sucks. My car got hit by a garbage truck twice in 2 years. So moving along to asking around to see who needed a one bedroom. The distant cousin of an Ex of mine said she needs it for herself and her two sons. (Doesn't matter to me how many people will actually live here, not my problem.) She asked me how much your asking for. Before she even seen the spot. I said 2 months rent. At $1,425. She came to see it and then decided she wouldn't take it and so I returned to looking for someone else. Now over two weeks later she calls and asks if it's still available. I said yes, and she said she needs it asap. For me to start looking for another place so she can move in. I said ok. I just need to tell her I want/need 3 months rent at $1,425. Signing lease over to her. But she still thinks I'm asking for 2 months rent. How can I tell her I'll be needing 3 months rent not 2?? It's expensive to move and I just can't hand over an place in a great neighborhood for so little. She knows how hard it is to find a decent place in NYC. I found a few places but with brokers fee (one month rent). I won't be coming back to this apartment. She can stay as long as she likes and move when ever she wants keeping sofas (red leather) and finding and charging someone else money to move in. How can I tell her In a friendly but stern way that I need 3 months not 2. Thanks in advance