I’m thinking of taking my grandmas dog

I rarely see one of my grandma, cause I live pretty far from her, and she has a dog who’s 14 and cannot take care of her. The dog, before it was in her hands, was supposed to go to my cousin, but she didn’t take care of it at all so it went to my grandma. And the way the dog is living is terrible. The dog has never been to a vet, is actively sick, and she gives the dog human medicine. I’ve seen her cut the dogs fur with scissors and nip at her skin, she doesn’t walk her either so she pees in her cage, she washes her with bleach, never dries her so she can get sick easily, when she’s out, all she does is cough, non stop, and from that alone, should show how bad of condition she’s in. My grandma says they do this where she’s from and doesn’t listen to me at all, so I suggested that she should put her down, give her to me, or take her to the vet (I said I would’ve covered the expense too), and she said knows how to take care of a dog (clearly not), and that I was disrespecting her in her house. My mom told me when I was younger, that when she would visit the dog, she would beg my dad to let her out so she can take care of it and say she ran away, but he never did. I’m now thinking about doing the same so I can take that dog out it’s god awful condition. I told my sister over the phone and she says that would be rude to take away the dog cause my grandma really loves her, and it’s not her time to go. I think my sister is dumb asl and I also don’t care at all that she loves that dog cause she’s in the most awful condition ever. I’ve had childhood dogs, still take care of them, and I’ve volunteer at shelters. I’ve taken care of different dog and cat types, so I’m SURE I can take care of that dog better than she does or put the dog in a shelter and visit regularly. But I just wanted to rant about this, and wanted other’s opinions. What do you guys think?