Legal Question in Family Law in New Mexico

There's a lot of information missing from your description but I'll try to fill in the blanks. A couple of hours with a lawyer might be worthwhile.

You've already taken the action you need if, as is usually done, the agreement you made was part of a marital settlement agreement that was signed by both of you and filed with the court.

That constitutes an enforceable contract. If it is referenced in and made part of the divorce decree it is also a court order that can be enforced through the contempt power of the court.

You don't say she is actuallly planning to sell the house but if she is you may be able to work out something with the escrow agent where you sign the quit claim deed as part of the closing. If the divorce agreement requires you to sign a quit claim deed you must do so (they usually require you to sign all documents that will implement the Marital Separation Agreement), but if it doesn't then by refusing to sign it you will have made it so she can't sell the house without your knowledge. That could be a little rough on her if she doesn't sell it for a while and something happens to you so it would be more reasonable for you sign it in exchange for a contract if the agreement I mentioned above has not been done.