I am the elderly sister of a sister who says she is POA. I have never seen the paperwork drawn up. Am I entitled to see proof of her POA?

She has hired 3 caregivers to take care of my fathers needs who has dementia. She recently quit her job & says she will be taking care of him for 2 weeks suddenly telling the caregivers who depend on this job. She has hired & fired many of them because she is a narcissistic person who if she doesn’t get her way she will fire. Also she leaves my father @ night by himself from 9:30pm to 8:30 am. Also I suspect she is dipping into his money. How can I prove all of this? I do have some proof but need to know how to prove she is taking money & going on many extravagant trips with her daughter of 23 yrs. She tells me nothing. All of this is happening in Johnson city, Tennessee but I live in Richmond & visit often & have noticed many things disappearing. Please help. I don’t care about the money except for my fathers needs which concerns me that it will run out because of her using the credit cards & he will have to be put in a home. Regards desperate sister who needs help on going the direction I should with all these concerns. Thank you.