How can I help my mother with dementia who has depression?

How can I help my mother? She is 88 yrs. old. She used to be a really sweet lady and down deep is still is. She was a great mother while I was growing up. Now she has dementia. These are her symptoms: she repeats herself all the time, she won't wear decent clothing, she wears dirty clothing, she lives by herself about a mile from me. She sits in her house all the time with the drapes pulled and the lights off. She won't water her lawn, she has ug sprinkling and has disabled it. She has so called caretakers come in every morning. She has turned the ac off and won't use it. The house is hot! She is nasty to the caretakers. She used to wear makeup and took pride in her looks. Now she won't put makeup on. She still goes to the beauty shop but apparently not enough because her hair is not good lately. She has stopped driving and rarely goes anywhere and no one visits because she is so cranky. I visit once a week.
So this is what is going on. I am old as well. She had me at a young age. My husband has dementia as well. His driving was so poor that he drove me in the path of a big truck and I became disabled because of the accident. I had to go to part time work. I just don't have the energy to do much for my beloved mother, nor can I tolerate the stress. I am in constant pain which the doctor says will not be going away.
My sibling is in charge of Mom. She is not doing much for Mom and rarely goes to visit her. She lives in the same town. Mom has plenty of money.
I would like to see Mom open the drapes, put makeup on, listen to music, quit being so cranky, get her hair fixed, wear nice clothes, use the ac and sprinkler. I would like her caretakers to take her to outings. If I suggest this to sib, sib says no. Mom has essentially given up. I just can't help her much. I have a lot on my plate, a job, a husband with dementia, and ailments.
What should I do?