You won't be responsible for your mothers medical bills as long as your name is not on the medical bills.
If it's just your mothers name that is on the medical bills then no one else but her is responsible for paying those medical bills.
If she has any estates such as a home or any other belongings then after her death the bill collectors could come after her home or any other assets to pay back any medical bills owed.
That is unless she gets the home and any other assets put in a will so that they go to her kids or kid when she dies.
But don't worry you don't need to pay any of her bills including medical bills when she dies.