If the balance owing on the reverse loan is higher than the value of the home (underwater) then it is very likely that the lender will ask you if
you would like to give them a "Deed in Lieu of Foreclosure". Neither you or the estate would be responsible for any shortage if the home sells for less than the balance owed.
If the Home Value is higher than the loan balance, the heirs would be able to sell the home and "keep the change" or payoff the loan with other funds and keep the home.
One thing to make sure of is that your mother has taken care of the succession of the property. Does she have a trust and was the property deeded to the trust? If she doesn't have a trust, does she at least have a will? When she passes away and the loan becomes due and payable you want to make sure that the heirs have the legal authority to sell or refinance the home.