Abusive grandmother. What do I do?

Hello. I've been trying to find answers and help for my issues for a while now, but with not much luck. My story is a long one, but I'll try to explain the situation in short. My father has always been taking care of his mother, despite her having another son (whose daughter she's also raised because he didn't want her). She's always been manipulative and controlling, always trying to keep him away from me and my mother as much as possible. January of last year, she had to come live with us, since she is 82 and the house she's been living in has deteriorated. The problems started immediately: she doesn't maintain personal hygiene whatsoever, she doesn't even wash her hands after going to the bathroom, she smells horribly because she refuses to bathe (none of that is new, she's always been like that), the whole house smells awful. If she pees her underwear she puts it on the heater to dry. At the dining table she moans and farts and complains about the food. All she ever does is talk about illness or other people's business, she has no interests or hobbies whatsoever. She demands to be taken to the ER for every little pain she has, it's gotten so bad my dad took her 15 times in a month. She's driven the doctors and the nurses at the ER mad. I also suspect she's addicted to her sleep and pain meds, and we've also found alcohol hidden under her bed. She doesn't let us clean her room because she's afraid we'll take whatever she may be hiding. If confronted with any of the issues (we mustn't even ask her to wash her hands), she'll throw a fit. She emotionally blackmailed my dad by saying she'll leave the house and he'll find her dead. She talks on her cellphone all the time, complaining to the rest of the family and telling them every single detail that's happened in the house that day. When she hears the postman, she runs to the street so she can take our mail before we get to it. She abuses the neighbors as well, to the point people are locking up into their houses when they see her walking down the street. She gets up in the morning, unlocks the door to the house and then goes back to bed so her friends can come on over without knocking. She can't walk very well anymore, but still insists on going outside, which results in her falling every time (she broke her shoulder a month ago, and today she banged her head). She doesn't listen to anyone. Two months after she moved in with us, my dad was diagnosed with cancer and she made that last year of his life even more of a living hell. She acted like he's not sick at all, demanding he takes care of her in all the ways he did before. He begged her to leave him alone a bit, he was in pain, but she had no mercy. She said she has every right to do whatever she wants to him, because she gave birth to him. My dad lost his fight three months ago, and now she's worse than ever because she's lost her slave, she has no one she can torture 24h a day, and there is no one who can keep her under control (he couldn't do much, but as little as he could it meant a lot). I live on the second floor and my mum has moved temporarily to the second floor to another apartment as well, since it's emotionally draining to spend time in the room my father has suffered so much in. She screams during the night and bangs with her cane on the ceiling, even though she knows full well I have to get my son to preschool in the morning and my husbands has to get up for work. If my son goes to the yard to play, she pulls out a chair, puts it in the middle of the yard and then screams that my son will accidentally kick her with a ball (she did that before as well). She yells at my son to come and put her in a diaper and will repeat that over and over despite being told not to (she's fully capable of going to the bathroom, but wants a diaper every night). I've been a wreck since my father died and after everything she's been doing to him for the past year I find it extremely stressful to be around her so I avoid her (I've been having chest pains and neurodermatitis so my doctor suggested I avoid stress as much as possible). She manages to stress me out just for the brief time I spend serving her a meal. She's also been verbally abusive to my mother since she got married to her son, but now it's gotten much worse. She's also been going around and telling lies about her being starved and asking for neighbors to call the police. If she's bored she climbs up the stairs and starts banging on my door, yesterday she didn't even knock, she just tried to break them down. We've been told there's nothing we can do about any of that. She made a contract with my dad 15 yrs ago so we can't put her in a nursing home. Her other son turns off his phone when she calls him, so he's no help either. We're not allowed to lock her in, but when she goes out she falls and my mum has to get off of work to go with her to the hospital in another city. I'm just so lost, I feel like I'm going to go mad..what do I do?