Anyone have tips on managing communication with my 85-year-old mom who calls me constantly, day and night, to tell me she is nauseated and can't go on?

Everyone here gave some very good suggestions. It's time to put a little distance between yourself and your mother. She is in AL for a reason. It is their responsibility to take care of her needs. Not yours.
Don't answer all her calls. Let her calls go to voicemail and screen them. Return the ones you want at your leisure. Or block her calls entirely and talk to her only when you want to call her.
She wants you to be at her beck and call 24 hours a day. Not only that but she wants you to care for her like a helpless infant and to also share in her misery.
If your health is starting to suffer because of your mother's miserable neediness and mental illness, then it's time for some tough love. Tell the AL they are the ones getting paid to handle her and make them do their job.
My mother is very much like yours except I'm her caregiver and we live in the same house. She has been mentally ill her entire life and it's always gone untreated. Now she is elderly and has some physical illness too. So life here is either like living in a hospice with a moaning dying person who can't breathe (this is one type of performance my mother gives for attention), or it is like living in a mental hospital. The hysterics, semantics, and lunacy is the other type of attention-seeking performance.
I finally got to the point where I just couldn't take anymore. She was working herself up into hysterics and hyperventilating. I told her that I have her POA and was calling an ambulance to take her to the hospital and that I would be having her admitted for a 72 involuntary psychiatric evaluation.
The hysterics and semantics stopped at once. She was able to get herself under control.
This is how you have to handle it. Don't play your mother's games. Don't share in her misery. Stop attending her attention-seeking performances. Your relationship with her will improve.

Ringing phones do not have to be answered. I think this is a generational thing... I don't even answer my phone if I don't know who it is calling.

You say she's in Assisted Living, so let them assist with her living.

Does the AL have a doctor who comes into the facility to see the residents? If so, I'd sign your mom up for him or her. It's a huge blessing for mom to be able to sign up to see that doc whenever she wants to, w/o your knowledge or interference, and if you are her POA, the doc can call you afterward to chat! That's what I did with my mother who also had all sorts of 'mystery' illnesses that were only visible to HER and nobody else. Such as 'rashes' that itched her uncontrollably but that the doctor could not see, feel or diagnose. So, after prescribing 20 different lotions and potions, she finally gave her an over the counter product she said would help. I, in the meantime, went out and bought her a can of Dermoplast which is a topical spray with lidocaine in it. Told her, ma, spray the spot that itches you, and voila, the itch magically disappeared. This went on for 2 YEARS by the way!

My mother was also chronically nauseous which had no organic reason to it, and ate Zofran like tic-tac. She eventually developed very bad vertigo to go along with the nausea, and car sickness too, so I had to take her to the ENT doctor dozens of times so they could perform the Epley maneuver on her, to which she'd have a super violent reaction every single time. I hired the PT/OTs at her ALF to help her with the vertigo, and they told me they'd never seen such violent reactions to PT/OT in all their years of experience working with patients! How do you spell histrionics?

Anyway, there are some things that lotions, potions, pills and doctors just can't fix. Have you tried Zofran for your mother? I'm sure you have. The last year of my mother's life, she was complaining about nausea constantly and I attributed it to her GERD. I asked her PCP to prescribe 20 mg of Omeprazole 2x a day, which she eventually increased to 40 mg 2x a day. That did the trick. The other GERD meds were doing nothing to address the situation, but I knew from personal experience about omeprazole.

If that doesn't work, you may want to give her a placebo type thing like tic tacs and tell her they've been proven to work wonders for nausea in elders.

Wishing you the best of luck with a difficult situation. I know that once these types of women get an idea in their heads, you can't chop it out of there with an AXE! :(

My mother-in-law would call every 5 minutes or so to say she had a headache. She was always a sweet woman so it was hard to tell her to take an aspirin and hang up because we were heading to work but she was driving us crazy UNTIL SHE WENT INTO A NURSING HOME. You Mom must have some dementia and forgets that she just called but still she can’t be allowed to drive you crazy. Is she on any dementia drugs? In assisted living does she always have access to a phone? Ask the staff to limit her phone use.

Its called "Do Not Disturb". I have mine set from 11pm at night till 9am in the morning. You can have just those on your contact list ring thru or no one. Mom will go to VM. Blocking is different, I din't think you get calls at all, the whole reason to block.

Maybe this is an anxiety for Mom. Or like said, a Med is causing the nausea. Is this something new since going into the AL.

Have you looked at the side effects for the medications she is taking? Nausea may be the result of side effects or adverse drug interactions among her medications. She is scared and knows something is wrong.

There are so many people on this forum tired to the bone because they are physically caring for their loved ones. It made me chuckle when I read you are at this same point … from … telephone calls?

Cell phones have all kinds of ways to be be silenced. if you can’t cope and you need to be able to use your cell phone, you can block her calls during business hours and unblock them whenever you wish.

Maybe it is the guilt that is really bothering you, not the ringing. Your mom is safe and receiving care. One day you will never receive another call from her ever again.

Listen to her on the phone when it is convenient for your schedule and you are emotionally capable to do so.

Better yet. Go see her in person and spend time together while you’re still able.

This nearly did me in, and I finally HAD to turn off the phone at times, especially if I really needed sleep. Mom finally figured out that I wasn’t going to answer every time the phone rings. Then she began to call less. You might pick a time to call her, then end by saying “I’ll talk to you tomorrow or Tuesday or whenever you decide you can manage.

Block her on your phone. Unblock when you want to talk with her, then block her again. She is safe in a facility. If there were a real emergency, the facility will call you. Go get some sleep 🙂

She wants to die because she nauseated? That sounds a little over the top.

A lot of meds will cause nausea. There are also a lot of meds that can allay the nausea.

Choose your battles. Block the incessant calls and take only the ones you can mentally handle. She sounds a bit of a drama queen, and that is one thing that is really hard to deal with.

You will have to limit her calls. Tell her you will accept her call early a.m. and one in the p.m. And that others will not be accepted. You have checked her out and that's great. You recognize she has mental issues which are not new and that is good.
I suggest you read Liz Scheier's book Never Simple. It will tell you how much worse it "could be". You will feel lucky. Mental health issues are always complicated, there is little support, and even when there is good support and the right "drug cocktail" is found, it seldom works for long. I know that sounds hopeless, but you have been here a while and know, and you will need to accept that you have to protect yourself. You will have to set limits no matter WHAT the repercussions are.
Best of luck out to you.