Should I call the cops on my sister for hitting her boyfriend?

My sister is 34, and her boyfriend is 42. They've been dating since 2010. I was talking to my sister recently. I forgot how it came up, but she was like "I've punched Justin before. I've I've pushed him too for being an idiot lol I can't hurt him." Obviously that's domestic abuse. I had a talk with him to make sure he's okay. He said everything's fine, and that he probably deserved it. I've witnessed him drive drunk before, and he has two dui's, but im not sure that warrants what she's done. I'm debating with myself whether or not I should report my sister.

Should I call the cops on my sister for hitting her boyfriend?
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