My mom has not been diagnosed yet. She has memory problems and it is difficult to see her like this. She thinks she is a horrible person.

Your mom's decline is both painful and heartbreaking to witness. You seem to realize that something needs to be done but you're at a loss to determine what. So you've got to get off of square one. Not knowing what to do seems paralyzing. Make an appt with a PCP or gerontologist to have her evaluated for her cognitive decline. There are many reasons for worsening cognitive issues, some treatable and some not. Until you find the cause you don't know what you're dealing with.

Apparently her will is complicated and difficult to figure out. Make an appt with an elder care attorney to help you decipher it. While your there, it would be very beneficial for the atty to draw up a financial POA and healthcare POA for your mom so someone can make critical money and healthcare decisions for her when she is no longer able to.

The best "added value" doc on my mom's medical team was a geriatric psychiatrist.

Dementia and other cognitive loss can cause chemical changes in the brain which often manifests as increased anxiety and fearfulness.

No amount of reassurance helped my mom. MEDS helped.

Please get your mother seen as soon as you can. Write up a bulleted list of her behaviors and thought process to give to the doctor before the appointment. Because she'll probably say "oh, I'm just fine"...