How to help suicidal/severely depressed person

My mom has been suicidal and severely depressed for a few months. She has been to the hospital, put on a 72 hr hold, and had numerous wellness checks called. To sum up her situation.. my 15 year old brother has threatened to kill her nermous times, tried to burn down the house, and choked her. She moved to her parents house and instead of surrendering my brother to the state, her husband chose to keep trying to fix his son. I live an hour away and have a 7 week old baby. I offered for her to come stay her for a little while, and help her get back on her feet but she won't. She is so far gone, there is nothing I can do or say to help her. She posted on social media that she tried to kill herself but it didn't work.

Any suggestions?