your not being unreasonable, this has to be dealt with. handle it just like a divorce talk.
i don't want this, i don't want your money, but we have to take care of this problem. i would avoid saying reactionary things like, well your name is on the mortgage as well.
turn it into a team building exercise. tell her the problem, ask for her advice, work on a solution together. it may just be the catalyst that you two need.
