Is there a landline phone for making 911 calls (but not the preprogrammed ones) that can't receive calls or make other outgoing calls?

ANY charged cell phone (with or without a contract) can make a 911 call.

That takes care of your answer but...
If she can not press an emergency button on a phone or on a necklace or bracelet maybe she should not be left alone.
Get a caregiver that can come in 1 or 2 days a week. That way you can get away when it is not an "emergency"
Introduce the caregiver to mom as a "friend" of yours.
"Mom this is my friend Betty. We are just going to chat a bit then I will get the laundry done"
You and Betty talk about the help that mom needs and Betty gets up to "help" you do laundry.
Later you can say "Mom, Betty, I forgot to get milk I have to run out will you two be ok for a bit?"
Then leave for an hour.
Mom will get used to Betty and and Betty can help mom by getting a drink or just chatting while Betty folds the laundry.
A day or two of this and mom will get used to Betty.

The choices are;
A. You never leave the house.
B. Mother stays home alone at times.
C. You take Mother with you everywhere.
D. Someone else supervises Mother when you go out.

It is hard when someone is dependant on you.

A. Is not practical or preferred (unless you love being a hermit).
B. Risk. How long is ok alone? Is she a frequent faller? Would she try to go outside? Cook? Do risky stuff?
C. Picturing running around during 6 errands in one morning.. Now please do keep up Mother.. Nope.
D. Less spontanious. Need to be pre-booked. Finding the right person may take a while. May even need a trick or fiblet. But don't write off option D. due to a senior tantrum of Mother saying no. It's for BOTH of you anyway.
For her safety + your peace of mind.

My folks have a regular afternoon a week sitter. Everyone knows the routine. *Someone* still tries to cancel every other week.. because they say they 'don't like it'.
They get anxious with sitters.. too bad. They fell when left alone. They lack insight about he situaion & are being a senior brat. The adult in charge needs to be reponsible & make the arrangements they need to.

You can talk to your local provider for control options. It has nothing to do with the landline phone you purchase. They make landline phones that uses large buttons with people's pictures on them to call out. Not sure about a 911 button...

If your Mom "...simply doesn't have the mental wherewithal to hit a button in an emergency" she very likely won't remember to call 911 on a landline that she doesn't use on a daily basis. My 95-yr old Mom is recently forgetting how to use kitchen appliances that she's used every day for decades. A phone is no different.

Also, what type of emergency are you imagining? Her most likely emergency would be a medical one, like If she falls -- she likely wouldn't be able to reach the phone anyway. Would she even remember her address to tell EMS?

At her advanced age and history of resisting adopting to new things, I don't think there's going to be a clean solution for her situation because a lot depends on her ability to learn and retain a new thing.

I just googled "phone with no dial" and several came up. This would prevent calling out but would not have 911 capability. 911 could be handled by the button on a cord service. Many of these offer the service of calling 911 and a family contact whenever the button is pushed as well. I would consider getting a new number that is unlisted that you only give to immediate family. This way you could call to check on her if you are out.

Yes, as already stated----Life Alert that is worn around neck. In our area, it runs approx $34.00 per month.

It seems to me you would be better off with an emergency wrist band or necklace , But the cellular hub for these devices, have a giant red button to push also. Good luck.

I have a friend - older who has dementia --- she doesn't want anyone to come in either. So this is what I did... I called a friend--- works as a caregiver, told her the issue. We came up with a plan that I would introduce her as a friend and bring her a few times and visit with my dementia friend. After about 4-5 times I left in the middle of the visit leaving them alone and my caregiver friend would casually start doing the dishes. The next time I left, my caregiver vacuumed and did the dishes. Then my caregiver friend showed up and visited and started cleaning up and my dementia friend has not complained once. It has worked out great. Maybe you can call a friend or Visiting Angels and explain the situation and get them to work with you. Blessings

I have a phone issue with my mom also. She’s got an ATT landline which they call a digital phone. I had to create phone blocks where only 20 #’s would ring in or out and those are myself/siblings and friends/family. I had to make the blocks bc she would pay a single bill 3 or 4x a mo. All utilities, business type things now have my contact info bc as you said, it is problematic for sure. My mom wouldn’t answer the call but she would write down the number then call me wanting me to google it finding out who it was. I’m not talking once twice a day, I’m talking hourly. They have several different blocks you can add if you have ATT, but I’d imagine other co have similar types. Good luck bc I know the phone thing is a pain..

I'm wondering how incoming and outgoing calls are "problematic".

Will she know to call 911 in an emergency? And will she know how?

If this is your desire, you can turn the ringer volume off on a typical landline phone.
At least when I last had one. Then, No Incoming Calls.

Is it a problem to be able to make outgoing calls?

You might consider investing in a "Life Alert" type pendant, or device which sits on a counter which only makes emergency calls. But there is a monthly cost, because the calls get routed to the company's call center, then directed to the appropriate responder.

Another option would be to install a camera in the house so you can look in on her when you step out. It will also allow you to talk to her, which would be nice, with no phone for incoming and outgoing calls.

Give Her a cell phone without a plan. It will be able to call 911, but nothing else.