Mom’s health recently took a turn, and I know my aunt’s mania is making things worse, but she’s the only family nearby. Mom refuses to put any legal authorities in place, so I am not her POA. Plus, I’m so far away. I knew this day would come, but I’m so unprepared. What can I do?
I agree you should report her to her county's APS.
You're not unprepared. Your Mom is.
THIS.
Unless Mom is deemed unable to make decisions, Mom can change her mind at any time & arrange legal documents to appoint a POA, a Medical POA/decision maker, list Advance Care Directives. Or not. Some never do.