u/contich13

This feels like true psychological warfare. That's not only OP's niece now, it's a daily reminder that she'll never have here daughter back, almost like she's been replaced. It's so sad. Sister is a pos. NTA

ESH - It's fine to expose him to your friend. It's not fine to tell her to act on it. You showed her what he is truly like, now it's on her to decide what to do with that information. Either way, she either knows he's a pos and is going to ignore it or she might also have been taken by surprise. IMO I would start to distance myself from the both of them. Anyone who can tolerate this kind of behavior from their SO is just as toxic.

Thanks man! -Tito