Sister "caring" for Mother with middle stage dementia will not answer phone or door. Has anyone dealt with this type of situation?

I have written on here before. Long story short, my Mother has lived with my sister for 15 years raising her Grandchildren , now (14 & 15 yrs old) because my sister claimed to have "Cronic pain" when really she has been playing the state claiming depression, panic attacks to collect money form the state, and abusing the money thats given. Recently after recovering from breast cancer, (which my sister hid from us siblings as well) my mother develped dementia, and at 78 years old is now being "cared for" by my sister. She picks and chooses when she will allow me to talk to my mother. Wont answer phone if she gets upset with me for ANYTHING. I live 4 hours away and I am working two jobs just to make ends meet in an apartment. Now will probably need three jobs. Caring for my Mother is not an option for me. I have not seen my Mother since January. Sister got mad at me because my other sister tells her things I have said about her. Now here we are again, she will not answer the phone. I called hospital my mother was admitted in in Dec, to get her Doctors name which my sister has never given me. They will not give my any information. I also called social serv. whom have been working with my sister to afford housing and making sure she is no longer drinking, and they told me they cant help me and I need to call police to do welllness check on my Mom. Which I did. My sister and nieces would not answer the door. They told me nothing looks concerning from the outside that they could see, and they will try again later. I was shocked, that they just walked away! So now what? I have no money for a lawyer at all. I am 4 hours away. My Mom was in Hospital with a SEVERE UTI last December and found she had 5 layers of unchanged adult diapers. My sister does not take care of her. She makes her teenage daughters do it because she still claims to have chronic back pain. Sits in her room all day directing orders to her daughters and smokes cigarettes. When social services come for a monthly meeting with her, she has her kids clean the house, and she gets out of bed and plays for the state. I am beyond upset and livid. She used my mothers life up dry, and now can't even take care of her proper and do her that justice. I have fought with my mother in the past to move out of my sister's apartment, to live her life, but because we had an abusive childhood at the hands of our father and my mother never left the situation, she feels guilt, particularly for my sister because she suffers depression, panic and anxiety and chooses to sit on her bum, not work and collect money from the state. all of us siblings went through what she did, and we are managing except for my brother who is homeless and addicted to drugs. But for some reason, my Mother felt obligated to my older sister, first born. It didn't help that my sister had 15 years to guilt my Mother and manipulate her. My mother was a huge enabler of my abusive alcoholic father, and when he passed away, she moved right into the hands of my manipulative sister. I am feeling defeated. Scared for My mother especially with the coronavirus going around, and am completely shocked the cops would not do more than knocking on the door. Has anyone dealt with this type of situation?
She has been doing this on and off for the better part of 3 years. I am making myself sick over this. Just got out of a bad relationship of 17 years and now having to start my life over is hard enough. I have an 18 year old daughter whom I share with my ex. He is a narcissist, and emotionally abusive. which adds to stress in my life right now. I have never had my Mother in my life because she was too busy catering to my father, and then my older sister. I could walk away from this, but I cant. My mother's life has been destroyed by abusive manipulative people, and now to top it all off, she is being isolated and kept away from her other children at the hands of my sister. So sick to my stomach.