What can i do to help her?

my best mate is having terrible problems at home her mom has left her dad for another man her dad is forbidden her to see her mom but she has manged to get her dad to let her see her mom but then she found out her moms new boyfriend strangled her sister now shes to scared to see her mom and when it went to court her mom took her boyfriends side and her dad is having anger problems a couple of days ago he threatend my best mate with a knife saying to her if you see your mom again ill kill you she came to school in tears