Advice On A Rather Odd, Kind Of Gross Love Triangle?

Okay so my grandpa and grandma both live in the same house, and my grandpa only moved in here recently because his Alzhiemers is increasing in severity and he must be watched all the time. My grandpa barely recognizes my grandma, at first he didn't believe us when we kept telling him she was his wife. We litterally had to show him the wedding photos. Now both grandma and grandpa go to seperate senior centers like, 3 times a week. Turns out, grandpa is currently dating a woman that goes to his senior center. My grandma is furious about this, she calls the woman nothing more than "a gold digger". The "gold digger" woman calls our house constantly. Grandma is taking this out on my mother. Grandma gets angry at my mom for letting grandpa even go to the senior center. But mom doesn't want to stop grandpa from seeing the gold digger because hes very sickly and at a misreable time in his life, but my grandma is jealous and can't see past that. Theres no way we can make both of them happy.