I have been having a regular caregiver give Mom a bath once a week. We also have an alternate. She spends two hours or less and is done and gone, no issues. For the first time we had one of the caregivers spend five hours just "babysitting" Mom so my sister could get out of the house (she was relieving me while I was on a much needed vacation). The caregiver seemed to "hang around" before leaving and my sister wasn't sure if she expected a tip. I have never tipped the bathers so I am not sure if this is expected or not. We pay the agency to pay the caregivers. Thanks.
If she was hired to do a 4 hour shift (for example) and your sister came home before the 4 hours were up the caregiver might have been uncomfortable leaving before her shift was officially over.