Doctor assessment for severe dementia and a MMSE score of 2....what's next?

MMSE so it was a full Folstein test? A 2 is beyond low. I’d be concerned that it wasn’t administered correctly (like tester stopped mid test) OR your mom cannot do a Folstein due to primary language conflict. Folstein has an inherent bias against those who are multiple language speakers or those who had another language as thier primary or early childhood language as the test is done in English.

My mom had really top notch testing over several years at a Univ Health Science Center with full Gerontology Dept & geriatric psych Dept too. Teaching Hospital situation. Multiple MMSEs done. 1 time was way off due to it not being done bilingual which was done all the other times. The test doesn’t have to be totally done in another language but more the keystone words do.... so like “Here is a “yellow pencil” is said and then “Here is a lapiz Amarillo” or ”Aqui esta un lapiz amarillo” is repeated. Bilingual code-switching just on key words is ok. They can recall just fine in their childhood language but English is a bust. The older my mom got the more her memory was Spanish language oriented & surprisingly some German too as she grew up in a very settled by Germans area. This was a woman who spoke English like 95% of the time & only Spanish when family came over from the old country to visit or she visited them. She was determined via testing and physical notations (the flat footed shuffle) to have overall characteristics of Lewy Body Dementia & it was good to know as some drugs better for a Lewy (excelon) and some psych drugs are to be totally avoided. 
If language issues could be your moms situation, she needs to get it repeated.

What is your mom’s living situation now? Home with help or facility?

Is your question about what to tell people or how fast this will progress or both?

I would tell people exactly as much as you know. It must be obvious to folks that mom has some issues. As my dads dementia got worse I had a bit of a struggle getting other people to not try and correct him, quit playing DONT YOU REMEMBER, or try to convince him of something. 

Those folks who are regularly around people with dementia need to have a basic understanding of the illness. And you certainly can’t have anyone trying to convince mom that she HAS dementia.

I can only speak to my experience with my dad. He always refused any testing. We finally decided it wasn’t worth the battle. His primary doc said he had classic ALZ symptoms. I noticed changes in him about 7 years ago. At first I thought it was just old age but it soon became clear there was more going on. Short term memory was failing, his ability to reason about simple things was reduced. It was so long and gradual.

 Dad went into assisted living just last month and is pretty much just in the moment now. He’s on a small dose of Ativan, there’s been some agitation but he’s usually good natured and easy to divert. But he’s still pretty healthy and agile at 87 yrs old. He keeps the staff on their toes!

((((((hugs)))))) That must have been a great shock to you. I think you need further evaluations of various kinds to learn more about your mother's condition and what lies ahead. A geriatric psychiatrist or a neuropsychiatrist could diagnose your mother's illness better than a PCP, and give you a prognosis, and, likely, recommend treatment. I hope she would cooperate with them. My mother, after extensive testing was diagnosed with vascular dementia. She was given meds to help her symptoms, and we had an idea what to expect in the future. There was an awkward window of time while the testing was happening when she did not want family informed that there were any problems. Once we had a firm diagnosis and treatment established, I, as POA, was able to let family know what was happening. If you pursue further testing, I would let family know that her dr has identified some cognitive decline and that further testing is planned. It would be helpful to her to know what is causing the decline, likely some form of dementia, so that she can get whatever treatment is available. Good luck!