AIBU to want to walk away? Advice on putting things in perspective please.

[Authorinwaiting]

To cut a long story short my father died suddenly a few years ago and he was my mother's greatest enabler because he gave in to her for a quiet life.
My sibling is younger and single and has relied on my dad to help her out financially her whole life despite telling anyone who will listen how independent she is.

I've taken over the running of my mother's house paying all bills tending to maintenance and sorting cleaning etc. mother has dementia but is managing with carers. I manage carers and all hospital appointments, I've fallen into this role as no one else was around to do it. She's a very difficult individual and sister is very selfish. Refusing carer duties because she works and has a demanding hobby and I don't work therefore she and her friends think I should be doing it. (sahm of 4 husband works away)

A very close family member on my husbands side is very ill at the moment and husband is very upset. I'm trying to support him and so haven't been as "present" with my mother and sibling. They are aware of my situation and rather than understand they are both increasingly demanding. Mother finding lots of small jobs which need done now! Sister constantly texting about minor ailments. Stresses in her life usurping anything else happening to me.

I don't want their support I just want them
To leave me alone to deal with what's happening away from them. I've had enough. I can't deal with them. AIBU to cut them
Off or should I remember my responsibilities to them and suck it up?

You could either cut them off totally or simply say to the two of them - I will continue to sort out bills (which you can do from your home) plus XX (also things that are fairly easy to do around your children) and the rest can be for sister to do or she can source help from elsewhere with this.

You have a life and responsibilities too, and while I think we should look after our parents (within reason) when they are old as they looked after us when we were young, it shouldn't all fall to one person especially when another could easily help x

I think you just need to set better boundaries. Let your mother and sister know (not that your mother will remember) that since your husband's family member is sick and requires your attention, the bills will still be paid, the carers still sorted, but you will be present and communicating less for now.

When your sister contacts you with a minor ailment, let her know you are unable to help. If your mother's dementia is anywhere advanced, she probably easily forgets these 'jobs' that need to be done. Be firm and consistent.

Yanbu. Do whatever you need to do to get through this and support your dh. You have helped them enough and have nothing to feel guilty about.

Maybe set up clear demarcations for when you will be available, ie:

I can do these mornings and carry on with admin. As far as you can arrange appointments within your hours.
Shut sister down on her carping on, no need for any of your energy there.
With dementia, be as agreeable as you can manage, but only do your set hours.
Some people are shameless and they’re usually in the family! Be tough.
Put your phone on silent.