How do I find someone else to care for my boyfriend's mother?

My boyfriend and I moved in with his house bound mother over a year ago because she literally begged us to. We became her caregivers. She is 70 years old has stage 4 COPD, is on 2 liters of oxygen, has stage 3 kidney failure,has an irrevirsebile colostomy, has dementia and alzheimers, has a brain tremor due to alcohol withdrawal, has heart problems, is legally blind, when she has to leave the house she has to be transported by ambulance because she can't walk up or down the stairs because her leg muscles are too weak to support her, also due to NO EXCERCISE, she smokes 10 to 14 cigarettes a day, eats continuously, she's 5' 2" and weighs over 210 pounds, she's mean and hateful to us and calls us stupid and dumb, She has a visiting nurse and doctor come to the house and lies to them and doesn't follow the doctors orders. Thats just the tip of the iceberg . We can't do this anymore, The problem we are facing is that there is no one else willing to care for her because of the way she treats them. She has other children but they are unwilling to take on the responsibility like we have.There is no reasoning with her because she is TOO STUBBORN. She refuse to go into a nursing home, the other children do not want to get guardianship of her, and so here we are, being treated like S*** and don't know what to do. Advise please.