MIL mad we didn't call to check on her?

My MIL has been very sick the past 6 months and may end up dying. She's a poor historian and gets information mixed up easily so my husband and I take care of her appointments, meds, etc. My husbands an only child so he bears this burden alone. He's exhausted and scared to death she may die. Her response is to disregard everything he tells her and she listens to every piece of bad advice her sisters give her such as not taking her meds as ordered and not having tests she needs. Her family has a mistrust of the medical community (her son and I are both nurses) so they've turned us into the bad guy and everything we say is considered suspicious. y husband and I have 3 teen kids with big issues and some other major stressors goin on and m hubby is close to his breaking point. We got a chance to go awa alone for the first time in 4 years so we got away for 3 days. We called my MIL 5 min after we returned and she was FURIOUS that we had not called to check on her while we were gone. AND she informed us that none of her family could believe it either and she happily told my husband that his favorite aunt called him an *sshole for not calling. She's 60, takes care of herself, lives with my FIL, and is doing pretty well at the moment which is why we felt comfortable going away. I am SO angry that she and the rest of the family have turned my husband into a whipping post and he won't speak up for himself cause he doesn't want hard feelings. What should I do?