Caring for mom; How do you get a formal diagnosis?

We noticed a marked decline in my mom about 2 years ago. I think the problems have been around longer than that but became more apparent. We do not have a formal diagnoses yet but I’m thinking she has dementia. Here are some of the issues we are seeing. Any advice is greatly appreciated.

-paranoia

-making up stories, miss remembering things from recent and past years.

-short term memory problems

-hoarding

-getting agitated, frustrated and very irritable easily

-inability to organize, plan and follow through on tasks

-depression

-sleep problems

-hallucinations: she’s had 2 bad episodes that I’m aware of. 1 about 6 years ago and another about 2 years ago. The first one was so startling I thought it was a side effect of her ambien

How do you get a formal diagnosis. We’ve been to neurologists, therapists and psychologists. The vets we can get is she has mild cognitive impairment. What we are experiencing seems much more serious though.

Thanks for any help!!! We are very frustrated and terrified.