Does behavior vary?

Very normal. In fact my dad actually became paranoid delusional and finally hospice prescribed Depakote for him as he was acting aggressive and even violent towards staff. It seems to be helping and yet yesterday he became angry and aggressive but was calm as soon as he had his shower. It is part of the progression and it is sad to witness.
dont feel bad about putting your phone on Do Not Disturb at times. I had to do that before hospice was in place so I could have my evenings with my husband. I knew if it was an actual emergency they would leave a voicemail. Usually it was nothing urgent. My skin kept getting thicker as time went by

Unfortunately, your Mom is not in her right mind. She is not who she was.. It is hard to see someone you love become another person. Allow yourself to grieve and do your best to love her no matter how she behaves.

This is part of the dementia. Mood swings, outbursts etc. My mom and dad both had their share of the mood swings. My dad was more controlled than my mom. They were both sick at the same time with the same disease and systems. Some days were great. we all chatted about anything and everything, laughed, told stories of younger days, memories I will never forget. Than the wacko moods would take over. mom was bedridden but dad I could help lift into his wheel chair and roll him in to see mom. there were times that I had them together and dad would say he didn't know who she was. mom would say that wasn't her husband, it was a man who wanted her body. dad would say I would never marry a woman who looked like her. they would go back and fourth. I would sit there and laugh so hard. even though they didn't know each other at that moment, they held hands throughout there whole time together. after both of them rambled on and on speaking over each other constantly, I would say it was time for dad to go back to his room, and dad would say ok I love you momma and mom would say I love you too papa, and it was nice chatting with you daddy. and away I would roll him.
Caregiving for both my parents was very hard but I will always have the wonderful moments with them forever in my heart.
dad passed away, and mom passed three weeks later.
I miss them so much.

My sister who has Alzheimers went through the different moods - happy & nothing bothering her to accusing people of stealing things from her home! Another stage was a man looking in her window & her calling the police & having him arrested! Each time she would add more to her story!
In her mind it was very true & she was very upset!
Another time she would tell you about the deer in her yard
which was quite possible. ( she lived in the country) but she then would tell you she was outside patting one of the deer!
There are so many different stages of dementia that is so unique to each individual— not one person is the same! Some can be so angry ,some cry all the time, some just happy living in their own world! It is a very sad disease to have !

My mom's  Alzheimer's-caused mood swings could happen daily or hourly. She lived with us, and you never knew whom you'd be waking up to: a happy person, or not.  She also accused us of stealing  (the most ridiculous)  things from her,  like a cup of (decaf) coffee. That said, a family member was in a facility where some residents  did indeed come into her room and (unknowingly) tried to take things, right in front of our eyes. Their Alzheimer's-ridden brains didn't know any better. On the other side of the coin, Hubby went there 1 night to visit, and a woman (a resident) told him that she needed to get out of there. He calmly told her that he'd get someone to help her, which he did. Later that night, a neighbor's dog ran out to him as he was walking our dog, and he returned the neighbor's  (female)dog. He told me the night's events, and I told him that he rescued 2 damsels in distress that night. He said, "Yes, and all she wanted to do was role over on her back for me." I'm thinking, "I hope to God he's talking about the dog." I found that humor helps in dealing with Alzheimer's. I even wrote about our travails, "My Mother Has Alzheimer's and My Dog Has Tapeworms: A Caregiver's Tale." I tried not to take my mom's insults and outbursts personally, sometimes easier said than done.

Seems to be.  One day, or even one hour, my mom is "okay" then there is a change all of a sudden.  It is a Dr. Jekyll-Mr. Hyde personality.  It doesn't get better, but I have seen that it depends on who is around.  When it is just me, she is a whiney baby.  When it is others, she is Superwoman.  When there are others and me, she never ceases to point out my faults to them.  Lucky me.

Has she been seen by the geriatric psychiatrist or behavioral health Nurse Practioner who is affiliated with facility?

Yes, most definitely. My father was the same way. Happy and smiling, a kid in a candy store, loving, and sweet...then turned "Swearing, yelling, demanding" not himself at all person.

It is for my mother ( vascular dementia). She’s been on a rant for 2 weeks, no UTI or discernible cause. Part is progression, part is her personality. She’s easily frustrated, angry and afraid due to her condition but she’s also never been at fault in her mind EVER so it’s everyone ,aka me , to blame. It’s odd how it comes and goes. Sometimes they hide it better than others. IE at a dr appointment although even then she’s been uncooperative lately.
It does baffle me though how she can be so out of it she can’t remember a phone call or appointment on her calendar yet can spin an entire rant on how it was our fault, she was totally innocent if all blame. The narcissist personality remains stronger than the dementia in that one lol.

YES! - this is part of the overall issue - when they can't actually see X, Y & Z then those items must have been stolen & most often it is the person they are closest too [& remember the best] who they blame - my mom thought it was me but I started to bring her a treat each visit so I went from 'stealer of goods' to 'bringer of treats' & she remembers the most recent so I was 'bringer of treats' in her mind

When I say treats it doesn't have to be much a few timbits, mug of 1/2 decaf & 1/2 hot chocolate, a plant with showy flowers but what ever it is it should be noticeable & YOU place them in her hand with 'I brought you something' said not just implied - it helps her feel loved & then being loved is being protected too - mom often liked it if I shared something with her so be aware that it adds to their enjoyment to share something [especially a food treat] with a loved one - I would also bring cute paper napkins to tart it all up .... hopes this helps