SFS- Try and work on your own recovery of detaching and minding your own business about alcohol and her drinking. Follow your path. If she is drinking leave the room, house or town. Don't engage with her. Alcoholics will use any excuse to drink so I can almost gtd that she will bring out the booze to celebrate grandpas life.
My advice to you is let her do her thing. Don't help her if she gets drunk, let her make an axx out of herself if she wants. You don't need to help her in any way, she is a grown women. What you need to do is take steps to educate yourself about addiction and being a co-dependent. Don't make it so easy for her do what she is doing. I understand that you will have funeral arraignments to deal with now. Be supportive, but if she starts drinking don't engage.
Hugs my friend, do your homework about this terrible disease and you life will slowly come around.
I am sorry for you loss!!