Is it ok to let the family know I'm unavailable one weekend a month?

I think you might be concerned that Mom will go for a two week stretch without seeing one of her daughters if you aren't there and your sister isn't there. Am I right? If so, I agree with you! But if your sister won't be decent, even after saying she would, you can only do what you are able to do. You don't have a lot of choice- you are doing your best and that can include stepping away.

thecaringsister, we've all heard of helicopter parents so I believe now we are seeing helicopter children who worry about their elder parents. We feel we need to be on-call every day of the week just in case something should happen.

Does your area offer on-line grocery shopping with home delivery. Believe me, it is worth every penny for whatever the delivery fee would be. But some on-line services you need a minimum grocery order of $50-$100. Buy a month's worth if Mom has room to store the items.

As for doctor visits, doesn't the retirement facility offer transportation? Or do you feel you need to be with Mom at her appointment to be an extra set of ears to make sure Mom heard everything correctly?

I agree -- you have POA and are ultimately the only person responsible for mom's care. Since mom is already in assisted living of some kind, I assume you're talking about having a "weekend off", away from the emergency responsibilities, should any rise, over that weekend, and we're not talking about actually providing "hands-on" care or supervision. Your request is not unreasonable, but since you already know you have a good-for-nothing sibling, your chances of getting help are slim to zero. Take your time off anyway -- you are already showing signs of burnout, and aren't actually doing the physical work that often accompanies caregiving. That's not a good sign - you need a break and must take it. Mom will be OK, and if something does go wrong, you can handle your instructions about how you want it managed over the phone. If the facility mom is at doesn't have care workers available, hire a temporary caregiver for that weekend.

If you mean Assisted Living, there are already people there to care for her.
If you have her in an Independent Living apartment, maybe it is time to consider a move. Safety is always your first consideration. Forget about sis, move on without her input.

I can't imagine what your Mom needs on the weekend that the center would not provide. You can always make arrangements for a friend or paid provider to check on her once a day while you are away.

As POA, you can't force your sister to help. That is very poor of her to agree to something and then not follow through on her agreement. It sounds like the two of you need to revisit this previous conversation and see what is going on with her.

What exactly does your mother need help with on the weekends at the retirement center?