First, you are in no way, shape or form responsible for your mother or her financial situation.
If she should pass way, the same applies. Family members are not obliged to pay a cent.
When my ex-husband died he left a house in the arrears, several credit cards, medical bills and utility bills. I consulted a lawyer friend and he told me that we did not have to do anything. I knew that I didn't but I wanted to make sure our children didn't. They were only 18 and 20 years old.
The one thing I did do was to take everyone of his bills and send them a short form letter that he had passed away with a regular copy of his death certificate. The letter just contained the basic information and I left a blank line to write in the account number. The lawyer told me I did not even have to do that but I did it anyway just so the mail would stop.
One time a collection agency called and suggested that we needed to settle his estate. I told them that we did not have to do anything and to never call again. I think they did once or twice but then gave up. I think our daughter got a letter once from a collection agency and it had a bunch of BS about settling his debt which I promptly ripped up and threw away.
His house was foreclosed on and was auctioned off later.