There's a small surge of fear when he stops. Arya doesn't know if he's just inspecting her or if he's going to take a swing at her. Green-Bruce is unpredictable. Instead, there's that flicker of gentleness, and Arya smiles, hoping the smile will help the green go away.

It doesn't. He starts running again, so Arya starts running too. She's not sure how much more sprinting she can take -- green-Bruce is far faster than she is, and seems to never tire. "You're going the wrong way!" she shouts after him, panting. Arya has seen villages sacked, and she knows what happened to Winterfell. Hadriel might be a large prison, but she still doesn't want to see that kind of destruction happen here.

"Smashing this place won't solve anything!" Maybe an appeal to Bruce's science side will work?