It doesn't sound like you have a written partnership agreement with your partner, so you must see a real estate attorney for this one. There are too many issues to deal with yourself.
You also have to figure out how to stay in your home, or make other living arrangements if you find that you can't.
Please let me know if I can help you with anything along the way!
Best of luck to you, Debbie,
You MUST go to a real estate attorney immediately.
What you are trying to do can't be done easily. She wants money and wants to be off the deed but you can't afford to qualify for a new mortgage.
You need to find a way under the existing mortgage to make things works smoothly.