Pidonus here will very likely not like Gilgamesh much at all. She'll gladly help just about anyone, hero or villain, who asks for her help, whether to save Sakura or get the feather away from Gilgamesh. That said, while she's got some terrifying cheese she can do, she doesn't stand a chance against Gilgamesh and she knows it.

Sein, unless dragged into the thick of things by someone, is staying the hell out of Attleton. But her sense of goodness won't exactly make it hard to drag her in, and she still has her Inherent Equipment and Inherent Skill, which make infiltrating just about anything pretty easy if she wants.