My mother never cared much about me, she adored my sister. My sister can not take care of herself as she is a raving irresponcible addict. I take care of my mother but she really hates me.
She has dementia and gives away all my things to other people when she has a chance. I can not always get those back. I have my things in a suitcase with a lock on it.
She drives her car and does not want me to drive but the insurance allows me to drive it. She has accidents at least 4 times a year. I can not believe the insurer they are so so patient with her. At the moment the car is yet again in the garage for repairs. I can not do the basics in the house.
She will ask me to paint her shed. she will say that is what I should do and when my sister visits she does not have to do these chores as she is different. (it has been like that since I was small) When I paint it and I take a break for a tea she will hide the paint. Those things drive me nuts. She is a drama queen as well.
Hope you called the plumber for the water heater... depending on its age [like over 12 years old], sounds like it is time to replace. A 4-bedroom home only needs a 50 gallon water heater unless you all wash a lot of dishes, do a lot of laundry, take a lot of showers/baths, and the house is heated with central hot water heating coils.
Mom has dementia and is no longer safe to live alone. Don't ignore this, we recently had an elderly couple start a house fire and they did not know enough to exit the building!!!
Regardless of your sister and what she's doing, take steps to get your mom full-time care whether it's in home or in a nursing home and make a life for yourself. You shouldn't have to live that way.