Does anyone knows an attorney that could help me prove my siblings are wrong?

To find an Elder Law Attorney in your area, scroll down to the bottom of the page to the blue section.... on your left you will see ELDER LAW ATTORNEY, click on that link... then follow the article until you see a section where you can put your zip code.

As for your siblings suing you, if they are serious with this threat, wait until you are served with legal documents. Your siblings would need solid proof, papers to prove there was a theft.   Are you Mom's primary caregiver?  Make sure you have records of every dime spent for her care, and if Mom is paying you a salary that there is an employment agreement.

If you are served with documents, and you cannot afford an attorney, a Judge will appoint an Attorney to help you.

You prove them wrong by gathering up all the bank and credit card statements for the last five years. You may need a criminal attorney if you are investigated by police and charged with something.

First, make sure you are NOT joint owner on any of her accounts. As a POA, you can be a signer, but you cannot use joint accounts or add your name to any of her property. Keep things separate and keep good records.