With a lawyers help you can sell her the house. Transfer the house into just her name or put both your names on the deed. You could also set up a trust so you do not exactly own the house but have total control over it. But at your death the trust automatically makes the house belong to whoever you wish.
As I stated originally, with a lawyers help what you want done can be done. But sadly, it will also take some $$ to do it. Ask what your best options are long term. With estate planning issues in mind it is possible that paying more for legal papers now will cost much less later on.
The one catch would be the mortgage company. But as long as you can make the payments yourself what advantage is there to have her on the mortgage itself?
She would have to qualify for a loan (alone) at the amount you agree on the house AND have the house appraise for that amount if she was to get a new mortgage.