How do I encourage my sister? ? Long but advice wanted.

My sister is 25 she is great mother and person. She currently lives with my granny until the end of this year. She was working but my nieces "father" got her fired. This isn't first time he has done so. He is violent towards her and manipulative towards ny niece who is 5. They have joint custody of my niece. My niece has behavioral issues. My sister has had leave her last job numerous of times to go get her or sit with her. Well he went up my sisters job threatened people and banging on window. They fired her. He has shown up at our grannies house with a metal pipe with his girlfriend. My sister call cops they said was nothing could do because he wasn't threatening her in thier presence. She has take my niece out school every Wednesday to meet him at police station so that take my niece. Majority of time he doesn't show. When he does get her he fills her up with lies and hate towards my sister. He also doesn't take her school when has her. He is even getting county benefit for her. My niece doesn't live with him however in California for some reason which ever parent shows up first gets the 💰 and food stamps . The school and my nieces doctor has writtwn letter stating that my niece is in care of my sister. That have never met the father and attached proof to thier claims . However the welfare office states just going investigation into the matter. But ut most likely hell win because he came first. My sister fills out tons of applications every day. I can see in her face and hear voice that she ready givr up. We are getting ready go to court for full custody but she scared of him . He told us be prepared to burry another sister. She really trying feels like there no hope how she going find job and placr before years end. She can't get help from county because he getting it and using on himself and girlfriend. The last apartment she had the owner let her lease said go home he was affaid of finding my sister dead . He said wouldn't be able get over that. My nieces father had broke into her apartment and beat her come back took my niece. After he drooped her off at police station claiming that ny sister left her home alone. All because he decided wanted hurt her and go to a bar. Children services took my niece tge worker quickly came to see how evil he was . Finally case was closed. I am at lost of how help her. I give 💰 when she needs it .o I just wish something else i could do. My granny getting old and given deadline of this year end. Sorry about all the jumping around but please help.