Opinions? Alcoholic mother attending family function.

So yesterday was my grandmothers birthday so I called her today to say Happy belated. She then asks if I’ve talked to my mother because we had a falling out maybe a month ago because she’s an alcoholic, I said “no why?” and she then says that she will being going to my grandmas ceremony that’s in two days.. (My grandparents are renewing their vows) I had a falling out with her because her drinking is out of hand and has been for years, she denies it hard core & even my elderly nanny (her mother) saw it & had to move out. Now I don’t know if I wanna attend this ceremony because she’s going and my grandma seemed like she didn’t even care if I went or not when I said we might not be going now. 🙄