My husband and I have tried to take care of all Mom's needs for a number of years as well as my brother. After a quarrel that Mom brought on, she stated she was going to live with my sister. Mom seems content for now, but no contact from sister. I feel that I need a break from all the "drama" that Mom causes, (accusations, lies, checkbook, etc.). I no longer feel guilty, as I know in my heart that I did everything possible to make Mom happy and well taken care of, but cannot understand the treatment I am getting from sister. We have never had this issue in our family. We always got along. Just makes me sad.
I know with my sister in law, we had tried to keep a communication book so all caregivers would know what was going on. My SIL rips pages out of the book and constantly sabotages my MIL's care. She is a nut job! We heard from the live in her daughters even told her not to do that. We gave up trying to keep her in the loop. I am sure that is not the case with you as you sound very caring. Enjoy your respite..!
I pray this is not the situation in your family, but it sounds so familiar, that I thought I should share this with you - only a medical professional could tell you and your sister if this is what is happening and even so, diagnosis is not that easy in the earlier stages. Please read up on Alzheimer's and dementia, just in case as it will help you understand the behaviors and why this is happening. You will all NEED each other if that is what is going on. Do what you can to keep the lines of communication open.