I have specifically instructed her on several occasions that she is not to transport my mother anywhere in her car. So yesterday my mom (dementia, 84) calls my sister (sneaking) to get permission to go shopping. My sister is 8 months out from Covid recovery and has cognitive issues. Sister tells them yes and forgot we had agreed to no transportation.
Sitter is amazing to my mom, sister is afraid if I talk to her she will leave but I hate this dishonest behavior. Now my mom has a "potential" exposure so I am forced to quarantine from her house for 14 days. My husband and son in law are extremely high risk for an exposure. Help!
Your sitter did absolutely nothing wrong. If you wish to make it clear to her that the Sister cannot give permission then please do so. Sit her down gently and say "I have to tell you that I am the only one who can give Mom permission to leave the home for ANY reason. Please be sure she doesn't try to do an end run round to my Sister. I so appreciate you; I know you will be diligent in this. There are many in the family at risk for covid and some suffering its after effects". I cannot imagine that a lovely chat with her, gently telling her this, would have any bad effect on her at all. In fact it would clarify for her what you expect because right now clearly she hasn't the slightest idea. She thought your Sister could OK this.
Covid-19 further complicates everything.
Regardless of the POA situation you need to have a face to face or mask to mask conversation with the care provider and explain how serious it is that one she took Mum out against your expectations and two falsified the log book. Let her know this makes you question if you can trust the entries from other days and is also putting your family at risk of exposure.
Formally write her up and let her know her continued employment hangs in the balance.
Also offer her some tips and suggestions on how to deal with your mother when she is restless in the evenings.