Where to find help for legal issues of dementia aunt?

Contact (or pretend) the public guardian (or transfer to allocated pension weekly) to look after some or all of her finances and the other abuse should stop a lot because she cant be extorted for cash.

Medical professionals are mandated reporters of abuse, so your doctor is obligated to do so. However it is good that she saw an MD. My elderly aunt refused to have medical help and her "companion" took financial advantage of her. We had no proof of her mental incompetence!

Start by calling your local legal aid. They helped me get DPOA & health care POA for my dad. Currently they are helping me with a lawsuit. Discover card is suing my step-mother for defaulting on her credit card.

Adult protective services are a resource.

Doctors are also a good resource. When my mom took my abused elderly aunt (aunt was abused by my cousin) to the doctor the doctor told her that he would be reporting the abuse to authorities.