Is it difficult at home?

Hello, I am 16 years old and have a friend who is still 15 and will soon be 16.

Of course, she has suffered a severe blow of fate, as her first husband, my friend's father, died, and then her second husband, with whom she also had two children, also died.

Since becoming a single parent, things have regularly gotten out of hand. She hits her children (16, 9, 6). She no longer works and is regularly very aggressive, especially towards the eldest, who he no longer knows how to control. He stays home as little as possible and tries to distance himself. What should I do? I'm completely lost.