My sister obtained power of attorney over our mother's affairs. I'm helpless...

She did this in a really sly manner. Excluding myself and older sister. Mom was declared compos mentis by her lawyer in order for my sister to sell her home. Which she did without telling us what she was doing. To start at the beginning of this nightmare, she was absent from our mom's life for a long time. In this time, everybody else assisted mom with chores, as she was becoming weak. My husband and I lived with mom for a few months and paying rent of course. We did her shopping, laundry and other necessities. Out of the blue one day my sister barges in and accuses us of living there rent-free and of stealing mom's money. She demanded that she takes control and already had signing rights on mom's bank account. Accused us and other family of having done absolutely nothing to assist. Moved her domestic worker/unqualified carer in and told us straight that everything said will be conveyed to her, as she has the power. Mind that at the time mom was still mobile with a walking aid, cooked her own lunch, etc. Sister and "carer" enabled her to become bedridden. She obtained a lawyer(paid for with mom's money) to get POA. Said lawyer declared mom compos mentis without any psychiatric input and put her house up for sale. Mom was unable to make her signature for 2 years before this and had dementia due to a pituitary brain tumor and a few mini strokes. We were not allowed any info on everything happening. Sister started throwing out mom's possessions and selling her furniture. When mom called me to complain that her photo's are being thrown in the trash, she was so petrified of my sister lashing out at her that she told me to please not say anything. The last time I visited her in her house, she was suicidal. My sister moved her into her house. Not even 2 months later, mom suffered a major stroke and her kidneys started failing. My older sister contacted me to say that mom is not doing good and I went to her the same day. Get to evil sister's home and denied access to enter. Her MIL and domestic worker shouted abuse at me and threatened to beat me up. Same happened to my older sister the week before. Got to see mom when I asked my husband to get the police. I could hear that she had fluid in her lungs and she was in a semi-coma. 3 days later mom passed away(last week Friday). When called to say the end is near, evil sister has the gall to say that I am allowed there to say goodbye. I did not want to see mom die, as I could not fathom the idea of witnessing the fake mourning and was of course called cold, uncaring etc. I have been ostracised and written off by even my older sister and my daughter, because I saw the callousness and evil intent of younger sister when nobody would believe me. She has always hated our mother and most definitely planned everything for greed and glory. Why else was she so adamant to get the will moved to "her" lawyer. She also lied about proceeds of house sale. Was informed that after funeral service, the social gathering would be at her home. From which I was banned for no reason. We still have no idea what she has done with mom's money. I said all along that I don't care for inheritance, but the fact that she is self-entitled to everything, has me in disbelief. Oh and I did enquire about having her POA revoked. Only to be told that without solid proof, nothing can be done. So once again, I have been shunned as the empath scapegoat and she literally got away with manslaughter. She has everybody twisted in her web of lies. At a total loss. Have never experienced betrayal, elderly abuse and grief all at once and I'm helpless.