90 year old Mom lives with her maltese puppy. Any advice on her "care" of the dog?

My mom will be 91 in a couple of months and lives across the street from me.
When she first moved here (at the age of 86), she purchased a little maltese puppy. It's a great dog, but the problem here is mom.

Mom says "Bella" refuses to eat dog food and she literally sustains her on 'treats'. I know this is not good for the dog's health. While the dog is not overweight, (Bella eats healthy expensive treats) I go in mom's house and find pieces of dried chicken on the floor, dried bits of banana slices, bones, etc. If I look in the kitchen I see 4 bowls filled with dry and wet dog food (thankfully mom changes this every day or two and the dog always has fresh water) - but I explained Bella is not eating because she is like a guest on the Carnival Cruise line with a buffet before her 24/7. In order to train her to eat real dog food, mom must TAKE UP those bowls and ONLY put them down 2x a day for 1/2 hour each, according to the vet and the groomer.
Mom refuses.
Additionally, the house stinks like piss because mom has pee pads all over the place and bella is one of those dogs, where if you come inside the house and lean down to pet her, she squats from excitement. Not only has mom drenched her booty socks walking on her slick white tile floor from the pee, but she doesn't always see it to pick it up.
Mom spends quite a bit on treats for Bella, and grooming 1x a month for her as well.
I don't know; I am venting today. She never should have gotten the dog. She would have done better with a cat. I have 4 cats myself and I certainly can't take her when 'the time comes' and I feel overwhelmed that mom will not listen to the vet or the groomer.
She considers Bella "A Person" in her eyes with her mild-moderate dementia and frankly I worry she is going to trip over Bella someday, as her gait is unsteady (like a drunk) at times....she gets dizzy and lately has been weak. Mom also has about 7 DOG BEDS scattered all over the house. One is a big bed like a victorian dog sofa bed and mom put a pillow down for bella to jump onto her bed... the pillow was on the floor in the living room and don't you know mom tripped over it, fell flat down. Thankfully she wasn't hurt.
I go in there, move the beds out of the walkway areas. I come back the next day she has re-placed them all where they were; right in the walking areas.
What to do ?