How to remove someone from a mortgage and title?

My fiance and his mother are both on the mortgage and title to his (their) home. The reason for this is that after her divorce many years ago she defaulted on the loan and it was nearing foreclosure so my fiance paid off what was owed and had it refinanced and put his name onto it so that he would have part ownership since he then took over all the mortgage payments and household bills. Now, almost ten years later, his mom is refusing to move out of the house (she has a home in another state, and had planned to move there, but since there is no one there to pay her bills, she's refusing to go) but that is neither here nor there. What we are wondering, is if there are any steps to getting his name, or her name, off of the mortgage and loan.

From what I understand, one of them would have to refinance into his or her name only. My fiance has the financial means to do this, but does she have to agree to it in order for it to happen?

She keeps telling him to just leave, and he'd love to do so, but she has no job, no money, no source of income and cannot keep up on the payments, so when it all goes under it'll mess up his credit as well.

Is selling an option? Would they both need to agree to that?

Are there any legal ways to resolve this? I doubt since he's been paying the payments and all bills given that they are both listed on the mortgage and title, but my only dealings with real estate have been with me buying under my own name and later selling, I've never had a joint mortgage or title.

Any advice or information is greatly appreciated! Thank you.

Not a happy family situation.

The telling part of your post is the word "their". She is part owner of the property, and lived in it before the son moved out. In law (her name on the legal title) and in equity (having owned the house previously, and presumably paid part of the original purchase price or mortgage, or by court order during the divorce).

I really see no way to force her out - selling, or buying out her interest in the property may be the only options.

OP, are you based in the US? If so, you should be aware that this is an Irish site and so we may not be able to advise on your situation.

Yes, I realized after I posted that this is an Irish site and I am in the US. Thank you for your advice though.