She used to love puzzles, reading, and was a pretty good artist. Her dementia is just bad enough for her to know that she can't think straight. She is able to live at home with daily assistance from my brother and I. She has very little contact with people other than her small family. She doesn't to go out other than to take a ride in the car.
If you google "Art and dementia", you'll get plenty of hits and sites to explore.
I would focus on music and art, even if you have to start drawing a bit yourself. It might help renew her interest. It doesn't make any difference what she draws; it's the process itself.
My loved one has a very short attention span. She can't do much with her hands, but she has been able to color a few pictures for me with the instruction from a staff member in her Memory Care unit. I was very surprised, because I had tried to get her to color last year and she would not. Something changed.
She can't carry on a regular conversation, but she does still enjoy listening to music, (oldies and country) attending church in her Memory Care unit (they hold a service in the dining room), watching sports on tv for a limited time, eating (she loves bananas, ice cream and biscuits) and holding her doll.
I put mom to work matching socks, folding underwear and towels on a rather large tray table placed in front of her, rolling up paper bags. My SIL had Alzheimer's. She enjoyed larger piec jigsaw puzzles. I'd sit mom down at the kitchen table and ask him to dry all the knickknack said wash every so often. I'd bring her with me into the kitchen and ask her to peel potatoes or anyhow I could think of that helped her feel useful making dinner.
You might consider getting her to daycare once or twice a week. 'Course that helps YOU as well.
It's hard...
Perhaps simpler puzzles than she used to do, or craft/art kits aimed at older kids, many of them are not too childish.
Listening to music seems to hold their interest long after they lose the ability to concentrate on anything else.
Are you able to take her out people watching? Sometimes just sitting in the mall with a coffee or small snack can pass the time and get you out amongst people without having to really interact with them, and you can stay as long or short a time as works for her.
Some others here have had a positive experience with day care, it gives them socialization and activities and gives you a few free hours.
My parents [in their 90's] would go out and do some yard work, and raking leaves kept them busy. I would see a dozen of yard bags filled with leaves. Of course, your Mom would need to be mobile and not a fall risk. Many a time a neighbor had to help Dad up out of the dirt when he fell... but that didn't stop him from raking leaves again the next day.
It sounds like your Mom still lives in her own place with you and your brother helping out when needed. Any chance of hiring a day time Caregiver who is familiar with dementia? My Dad's Caregiver takes him for walks in the neighborhood, and occasionally to McDonald's for something different for lunch. She tries to get him interested in doing different things, until he dozes off :)