This is driving me nuts! I can't have my unsanitary mother messing up the beds like this. She lies about washing her hands. Today I saw her use the toilet without wiping herself and went crazy. She won't change her briefs unless I carry on like a maniac. I really don't want to live this way. How to make her bathe??
Focus on what Mom needs.
More supervision, assistance, company?
That gap between what you can do & what Mom needs has widened. It will keep widening.
If you feel your siblings could/should be providing more help, step up to fill the widening gap - ask them directly - what they can & will do.
Although I think you already know the answer.. nada, zilch, nema.
Feeling resentful is a normal reaction. It can mean you are giving too much.
When the care needs increase, so must the care. When it outweighs a reasonable amount for ONE person, a TEAM is needed.
If extended family is full of non-helpers not fit for your team, widen your search - include NON-family to the team: home services, aides, daycare, sitters. (Yes it may cost. Mom's finances may need to be looked at here).
How does that sound?
Stop expecting anything from your siblings. They're probably just happy that they're not the ones caring for her. And you kind of can't blame them. You need to consider moving her to an appropriate setting be it nursing home or memory care.
You need to remember that your Mother's brain is broken, she cannot help what she is doing. Carrying on like a maniac will only damage your health, and scare your Mother.
As for bathing, it is also not uncommon for someone with Alzheimer's/Dementia not to want to bathe. For some reason they don't like the feel of water. They are also afraid of falling in the tub. Some get claustrophobic. There are caregivers that you can hire [with Mom paying for it] that deal with only bathing/showering a client.
Maybe you don't want to even consider this, but maybe it time for your Mother to move into Memory Care if she can budget for the monthly rent. If not, Mother can apply to Medicaid [which is different from Medicare] and they will pay for her care at a nursing home.