Is there another way for her to do her business without using a catheter?? I’m only 20 years old so I’m not her caregiver but I’m over at her house several times a week and it’s bad enough that I have to witness her do these things. I’m not supposed to tell my grandpa about it (he gets easily agitated mainly because of her) but I think he already knows.
You say there is a visiting care agency, that's good. And then apart from you, what other family members regularly visit and help your grandparents? Have you talked about this to any of them?
I cheerfully admit I'd never heard of myositis, but we learn something new every day! This link - https://www.myositis.org/patient-support/living-with-myositis/ - is from The Myositis Association and may be helpful if you haven't come across it before.
Who is cooking the meals? Cleaning the house? Doing the laundry? Is everything on your grandfather's shoulders?
You say she is "nearly paralyzed" but what does that mean? Can she walk, or is she in a wheelchair?
And where is the wine coming from, since from what you describe she couldn't possibly be going out shopping on her own?