When is the right time to ask for the removal of sister's POA over mom (85) with dementia who lives with her? Sister has addiction to thc.

I have moved with my mother from Iowa to my sister's home four years. She is a medical profession, a home healthcare pt treating mostly elderly patients. I expected sterling care from her and to be allowed to participate actively in her medical and daily life. I am the youngest and have a strong relationship with mom. My brother before our move, and having control of her estate as poa, diverted $100,000 from her savings to pay for my nieces wedding and cover bills at his poorly managed pt clinic. We are now estranged from his family. Sisters family is rife with substance abuse issues; she has smoked marijuana daily since college and does so sometimes while between patients. She lacks any insight into the nature of her behavior. She and my brother has gaslighted and scapegoated mom and I for two decades, entirely unjustified and guided by misperceptions, biases, and supported by numerous conginitive errors and fallacious logic. My education is a b.a. in biology and psycholgy from luther college, but since I didn't get into medical school I have since been treated as a failure although I became a mainframe consultant analyst at fortune 500 companies. Their gossip, maligning, of me and callous disregard have continued since. I was diagnosed with add and bipolar 1 during my divorce and lost custody of my son because their family was very wealthy and it was a fight to the end, a zero sum game. I became suicidal and had to stop the fight and give up my son to survive. The next ten years were a living hell with repeated episodes of nearly fatal manic and depressive episodes. My family heavily stigmatized and our relation deteriorated. Mom and I began being gaslighted and scapegoated, which affected both of our mental and physical health. Mom began being treated as a piece of furniture. I will never understand how our family became that way. Father passed away five years ago and I moved with her to my sisters home in Texas, expected excellent care from her of my mother. Although she had diligently helped with adl and clothed and fed here it became entirely my role to see to her mental health and happiness. My sister's house has a long history of family dysfunction. She drinks 3-4 glasses of wine and allows mom drink freely despite the fact the for ten years she had been advised to not drink at all or only one a day due to her parkinsons and dementia. They go out for lunch every other week and we have to help mom walk. I received my 3yr sobriety chip last week having received no support or recognition. Sister has surprised my by her steady mental abuse of mom through passive aggressive behavior, insults, childification, lack of stimulation for mom (usually leaving her to sit in front of the tv from morning to bedtime. My role is to provide her with attention, emotional support and attention, which I do 3-4 hours a day 4-5 five days a week, living 45 minutes away. Although being well fed and clothed she receives a paultry amount of physical activity and has lost 25 lbs since our arrival. Most disappointing and significantly sister has very inconsistently followed our primary care providers and neurologist instruction. She doesn't believe in pharmacotherapy and we have missed numerous opportunities to try interventions in her dementia and depressive symptoms, believing that they wont work, it wouldn't matter anyway, and they are more trouble than they are worth. Despite my superior education and my similar bouts with depression and insomnia she refuses to follow through the prescibed sleep medications and went a whole year without treating her copd. It's as though mom is here out of duty and mom is too much of a burden. My input and ability to help at the house and steadily ignored and remove. I am mocked by her for conversing with her as though she is still a person and am instructed to only talk with her about the weather. After an arguement recently I was told to not return to moms and move her home