Maryjo,
Sorry to hear about the split. From your post it would appear that you are both keen on resolving the mortgage situation so that is at least one positive.
If you sold the property, you would both be required to pay the shortfall. Although getting a personal loan each for the split of the balance may be a solution, you will pay a much higher interest rate on the personal loan.
The bank may be agreeable to converting the balance to a term loan, again at a higher rate, but it would probably be in joint names and any missed payment from either of you would affect the credit rating of both of you.
Your post says that they mortgage payment is greater than rent receivable, could the loan be switched to an interest only loan, even for the short term, so that rental income may come closer to covering the loan payment?