In episode 2, Florence doesn't react at all when Rob is hitting Jo in the kitchen, just carries on playing her video game. Not a twitch. When it cuts to Jo and the girls around the table, Jo is crying, Poppy is pushing her food around. Florence again seems unfazed and is eating. She only reacts when Poppy asks Jo why daddy hates her. And then it's more of a curious turn of the head to see Jo's reaction.
I don't believe the girls appear in episode 2.
In episode 4, when Rob returns home with the girls (clearly steaming at having to pick up again), Florence breezes in, straight to the TV. Poppy is hesitant and holding back in the hallway as Rob runs upstairs, before following Rob to the kitchen- instinctively knowing either something is wrong or wary that there's about to be a DV episode. Florence's only reaction is to side eye Rob as he steams past her to get to the kitchen.
Such contrasting reactions. I feel like it's been written like this for a reason. I know kids an bury their feelings in DV households (I know this very well), but the writers/directors seem to be deliberately having Florence show almost none while Poppy is like a mini version of Jo.