All of the comments above.
I was told my Father was terminal, from cancer, plus his heart was failing, too. Nothing could be done for him.
Almost 8 years later I was also told my first partner was terminal. And again, nothing could be done.
Sometimes you just have to be tough for them, even though it's ripping you apart. That is your duty now.
It's not about YOU, it's about HER, your Mother. You must sarcifice your own feelings and set them aside, in order to do what's best for her.
And sometimes, if you're dealing with a hospital, there will be counselors there to assist you. To advise you what to do regarding your Mother, and how to personally deal with this situation yourself.
When I lost my partner I didn't how to handle it. So I sought out the experts, never having been through this before, along with the support of friends. Frankly, it was more my gay friends who helped me than the experts, not having any family, but everyone is different You should look at doing the same.