What do you do when she can't figure out how to use the toilet or forgets where it is?

You might want to get a toilet safety frame. It will give her something to hold on to and she may feel less afraid of missing the seat with arms on each side of the toilet.

Onlyacaregiver from an elders point of view (without dementia but with physical limitations) I have become fearful of trusting anything I cant see behind me like sitting on a chair someone pulls out to assist me or stepping down off a step. I just have to look before I make that move. I wonder if putting a mirror in front of the toilet might be helpful. Haven't tried it but that just occurred to me. I do have my commode frame over the toilet to help me get up but am still reluctant to sit down until I feel the seat behind my legs.
My sister in law once said to me when I was late toilet training my children that eventually they will do it themselves. Yes thats true but does not apply to a demented elder.
There is no light at the end of the tunnel for caregivers, you just have to bring your own flashlight!

Take away all her panties and replace them with disposables, get the kind that look and fit more like underwear. And you might have to start helping her in the bathroom.

You gently sit her down and hold her hands and talk to her, just as you did with potty training. And you clean her up.

I try to talk to her but she keeps talking about how everything has to go down there and she points to the pant and then she talks how it goes into the floor. With potty training you can capture a child's attention with just talking to them butt with your 93 year old mother who does not want to be wrong and tells you that her going in her pants is my fault because I got her the depends is a little hard to smile through as you are trying to get her changed. But I keep trying knowing that some day all this will have an end and as she goes along in her final chapters of life. So sad it has to end like this. What a horrible way to go out of this world. All the things she did in life and this is what it comes down too.

You are right, onlyacaregiver, this is not really like potty-training a toddler. With a toddler you can be certain that eventually they are going to get it. Their learning ability and cognitive skills are getting better and better. They want to please you. It might be a struggle for a while, but you are assured of success. Your mom's cognitive skills and ability to understand are getting worse and worse. She may not be predisposed to want to please you.

So very sad that it is ending like this! Do everything you can to help Mom keep some dignity and to know that you love her no matter what.

You need additional help from a trained nurse, coming to your home, who can show you what to do, how to anticipate and how to support your mother. Especially how to manage her weight (old people can get extraordinarily dense and heavy for their height). Save up for two or three sessions with a private nurse and tell your doctor you need someone who can train you. This nurse might also be in a good position to advise you when to take your mother to residential care, even if just for a couple of weeks to give you a break.

I have to help my mother to the commode, I've given up on the toilet. I even have to wipe her. Safer for her and more room in her bedroom for me to help. I'm very blessed that she is usually obedient and trusts me.

I like the idea about getting some professional guidance, but, if she's not able to handle toileting on her own, I'd just focus on complete supervision. Like supervising her as she puts on her disposal underwear. And she has no other options. And I have read that adult onesies that snap in the back will prevent the person from being able to take their underwear off, so, you can attend to her soiled or wet underwear, when it's necessary and when you are in the right location. That, plus securing the bathroom doors so she can't go in there without you, and setting a schedule of when you take her in there and place her on the toilet. The support of the rails might make her feel more secure. It sure sounds exhausting, but, what other options are there? It's likely she is not going to get more adapt at this.

Depends has a pull up pant. My Mom actually liked them when the rehab had her use them. I find I like the Walgreen brand. Couple of dollars cheaper and they have coupons and buy one get the second for half price. They do start having problems toileting. I had Mom calling me when she had to go. If she went on her own, she created a mess. And yes, don't allow her to clean herself. She could end up with a UTI. I use buggy baby wipes because they are bigger and thicker than the ones for ladies.