What is the legal situation if my father-in-law is refusing medical attention and he is very ill? Can my mother-in-law be held for neglect?

My mother-in-law is taking care of my father-in-law. We believe that he has cancer. He’s been the type of man to never go to a doctor. He made my mother-in-law promise him that she would not call an ambulance or take him to the hospital no matter how bad it got. My poor mother-in-law is beside herself for she has been trying to do the best she can with taking care of him. He will not let anyone in the house other than her. The way that she describes the situation and him it’s horrible. He has horrible sores, he is defecating all over himself, he barely eats or drinks and we believe him to be on his deathbed. The guilt she feels for wanting to do some thing but not betraying her husband is horrible. She has begged him to let her call an ambulance or to take him to the hospital and he will not allow it. She has told her doctor about the situation because she is afraid that she is going to be charged with Neglect. She called my wife today and said that she thinks that he’s passing. His body is swollen from fluid retention and his breathing is shallow as though the fluid is going into his lungs. Scared for my mother-in-law, she’s a good woman and has been doing the best she can this past year taking care of this stubborn man.