Can anyone tell me the easiest or best way to verify my mother has dementia?

If these are new changes you need a physical assessment by an MD. You could be dealing with a bladder infections. OR you could be dealing, and it is more likely, with changes having to do with mentation. You say she lives in assisted living. She will have aids there and a profile. Discuss this with the person in charge in a one on one phone conference arranged at a time of their convenience and get an idea how to proceed. A neuro assessment can get you up to date with where you are, what probably type of dementia, what prognosis (they are VERY different, for instance the differences between Lewy's and Alzheimers). There is no way to know how quickly things will progress. There are no cures. Doctors today will prescribe any number of drugs. That I know of NONE are proven of benefit scienfically by any independent testing, and for instance Novartis has just settled on huge fine agreements because of the amounts they pay doctors to describe these drugs and others. So start at the beginning. Speak to the facility she is based at. I am assuming you are her POA. If not, this does fall into the realm of her POA. And THAT would be where you start.

Superman, a good starting point would be to take her in to be checked for a UTI and then at that time have the doc give her a cognitive exam. Urinary tract infections are extremely common in elderly women and can cause confusion and personality changes like you are describing. If she has one then antibiotics will clear it up and she may go back to being her old self. But UTIs often keep reoccurring so you'd need to be on guard for one. Also, you may need to be in the room at that time of her appointment, sitting behind her so that if she gives really inaccurate answers to the doctor's questions, you can indicate the right answer silently by yes or no head movement. This is what i had to do with my MIL. You ask if there's anything that can be done about her memory...I don't have much experience with that but I know there are medications on the market. These would only delay memory/dementia/ALZ symptoms, but they do not stop them. This is a question for a geriatrician or gerontologist (a doctor who specializes in elderly care) or for a neurologist. There is much for you to learn in order to be the best advocate for your mom. Teepa Snow videos on YouTube are very educational regarding aging and dementia. I wish you all the best as you help your mom.