I need advice on giving advice.

My sister and brother in law live 2 states away from me. Sis has been on dialysis for 25 years and really does not have good quality of life anymore. Her husband is her caregiver. A few months ago he texted me and said he caught her throwing away her meds. Today he told me he doesn't know what to do. She skipped dialysis last Fri, went Mon and skipped again today. That is one day in 9 that she went to dialysis if she goes this Friday. She has skipped a day here and there before, too. Dialysis center keeps getting after him to get her to dialysis, but he says he can't drag her by the hair to get her there. I really don't know what to tell him. I can't talk to her on the phone because she is almost deaf and she is legally blind. I think she must be starting to give up and I really can't blame her. I don't know if I could have gone through what she has in the last 25 years. But I have no idea what to say to my brother in law and he doesn't know what to say to her. Sister is 71. If anyone has any thoughts on this situation, I would love to hear them. As far as I know, she hasn't actually said that she wants to stop.