Mother that takes anger out on her kids

My mother in law is pretty okay most of the time, but I've noticed that when she's mad she says whatever she wants to "get it out" or takes it out on her kids- 
Example- she was mad at her husband for being out all day Sunday so when one of her sons (who is 16) who was just playing a VideoGame said "we all went out to dinner Saturday, maybe he felt that was enough?" And she responded with a "Shut up! You're such a fucking little prick!" And stormed out/-- 
Is this okay to anybody?? I've tried talking to her before but she says that's just how she is... That she doesn't mean it & laughs it off...
What should I do..?