how to talk to my alcoholic mother in law

Lizz
My future mother in law is a severe alcoholic. Like, her health is physically and mentally deteriorating because she barely eats or sleeps and is drunk 24/7. They have a hospital toilet next to her bed and are currently installing a hand railing for the hallway into the kitchen because she's fallen and hit her head on the granite multiple times in the past year. She's so far gone she will not listen to anyone about her alcoholism and she constantly says she's afraid I'm going to "fuck over her son" even tough she's never been given any reason to think I have anything but love for him. I'm getting to the point where I don't know how to talk to or deal with her. Has anyone ever dealt with someone in their family that has any advice? Im to the point where I'm about to start googling how to help your spouse with the loss of a parent :((