How can I have my sister removed as POA and use my Mom's income to care for her?

My mother has been diagnosed with Dementia probably due to Alzheimer's. She lives with my sister who has POA and is not caring for her. My sister is a hoarded and works full-time and my mother is alone 12 hours a day Monday-Friday. She refuses to spend my mother's money on care for her and I think she has been taking my mother's money. The house is filthy and full of junk. There are no clean clothes, dishes and rotten food in the refrigerator. My mother signed her house over to my sister 3 years ago and my sister is using my mother's money to pay all bills, taxes and any other household needs. There is neglect of the house maintenance too. The upstairs toilet overflowed due to mother flushing pads. My mother is eating cereal only. My sister says she is fine to be home alone. I contacted a home care agency and my sister refuses to pay for it. My mother has an income of $2,000/month from social security and a pension. She also has long term care insurance who will pay $92 per day. My sister agreed to home care for the amount of hours paid by the home care agency only which is about 4 hours. The home care agent came to the house to do an assessment and saw the condition of the house and said I should seek guardianship because of the neglect. I have contacted a hoarding task force who will come for free to clean up the house. My sister says she will clean up the house. There is also a male friend who I suspect is directing my sister to take my mother's money. I have read about what guardianship entails and I cannot afford it. I would like to become my mother's POA instead of my sister. How can I have my sister removed as POA and use my mother's income to care for her?