How can I get my sisters to be transparent with care and finances of my Mom?

It is possible my oldest sister has DPOA. My father set up a Living Trust, DPOA, Living Will, Will before he passed away. I would really like access to those documents to verify that nothing has been changed and when the DPOA becomes in effect. They may have taken it from the safe box. How can I get it. If she does have DPOA then I believe her secret loan is criminal. What if she isn't DPOA yet?There should be no personal benefit/gain from my mother's assets which, in addition, are in the Living Trust.

Does anyone know if a mediator could help? Does anyone have any experience with having taken that route?

Yes I do get that. Petty differences shouldn't matter. They've managed to get their way by having my mother purchase a 4 bedroom/2 bath house so my youngest sister and two children can move in with her. The issue started with even suggesting she pay rent. No matter, I had to gather some information on my own, which I should not have to do, and it is very likely they will be closing soon. I don't know if they plan to give us the new address or home phone number (which is necessary). When my brother has dropped in, he lives closer, they tell him to back off when they find out.

Obviously I do not have all the facts, I am certain there is much more to this. My first impression is your sisters are doing the hands on caregiving, hence IMHO the earn the right to make the decisions and I understand not welcoming distant quarterbacking. If they are doing anything other than using the money for her care they are wrong, possibly criminally wrong......but my guess is this may just be a difference of opinion. Under no situation should they be cutting you off from communication. Take a long weekend and drop in.

Sorry if that is not what you expected to hear, but this may be a perspective worth considering.

You hire a lawyer and get an independent guardian assigned in court.

Who has DPOA?