I Am A Caregiver For An 87 Yr Old Woman

I am a caregiver for an 87 yr old woman with some form of dementia. She is usually easy to deal with but the last couple of days her son has allowed her to drink wine. Not a lot but it seems that after a few hours she gets really combative. My question is should a dementia/alzheimers patient be allowed to consume alcohol? From what I understand she was a drinker in her younger days.