Should I say something or stay out of it

I saw my friends man with another girl at Walmart. He was grabbing her ass and stuff. I thought I should tell her, but honestly there relationship is so toxic I feel it would be pointless. She has cheated on him countless of times. They put their hands on each other. They are both equally abusive. She cheats on him, he cheats on her. They are literally arguing over the paternity of one of their kids 🙄. They have 5 together (at least thats what we think). Is it really worth the drama? I mean they both treat each other like shit. I get she's my friend and I should but I really don't know if the drama would be worth it. Last time I got involved in that B.S I had to call the police because they started getting physical with each other in front of their kids.