First question: Is your current loan assumable (such as an FHA insured mortgage) or does your mortgage or Note contain a "Novation" clause? If so, you can approach your lender about switching out borrowers. An application from the new borrowers plus a copy of the divorce decree and marital separation agreement will be required.
Second question: Have you called your lender to ask? If your mortgage or Note aren't FHA insured or lack a Novation clause, then you'll need a loan modification. The modification will add a Novation clause, allowing you and the lender to swap out your ex-spouse in favor of a new borrower. The challenge will be the occupancy type - your ex-spouse is currently an owner-occupied co-borrower; her parents as a substitute borrower will be non-occupying co-borrowers... which is a significant change in loan terms and not easy for the lender to grant.
Third question: Does your divorce decree (as it stands now) REQUIRE you to refinance to remove your ex-spouse? If so, you're most likely stuck with refinancing. If NOT (which is the usual blunder most attornies makes) your ex-spouse will still be obligated to pay the mortgage whenther you pay it or not. Some lenders will remove an ex-spouse from a Note if the spouse who gets the house can demonstrate qualifying ability to repay without the assets and income of your joint marriage estate (ie by yourself).
If the three items above fail, then you're left with a refinance as the posters below advise.