It is unfortunate your father didn't have the insurance on the house that would pay it off in the event of his passing but you can 't live life in reverse.
Any kind of refinancing she would be able to get would more than likely extend the time period of the loan to 30 or 40 years and/or change the interest rate (great for the mortgage company but not necessarily for your mom in the long run). You have to weigh the costs. They will factor in her age and life expectancy into this equation.
Would it be possible, practical, and or feesible for her to share the space with another woman around her age? Does she have any friends she could or would roommate with? Then she would have company or companionship and help with her mortgage. Perhaps she may also consider renting out her space to someone who needs space for an in home daycare. She wouldn't have to work at that business just lend some of her common space such as livingroom, bathroom, outdoor space and kitchen for use. She could use the extra income to help pay the mortgage.
If she is able to get the refinancing and even if she can't it would be in everyone's best interest to try to get the insurance that pays it off in the event of death. Makes for one less headache and if you choose to sell it, you have more leverage to get rid of it quickly if it comes to that.
I just love to think outside the box to see what else can be done outside of extending debt. I hope this helps.