Eliya is from Princess Pernet's faction, and boss's elder brother Gilius is a mole in that faction. Maybe he's a double agent instead? He's the spy? It's can't be that obvious, right?
Also, I'm disappointed the internal court faction opposed to the king is also turning out to be an enemy of the resistance, if Eliya being here is an indication. She's not so smart either, so that's even worse.
On pg. 18,
ポタ "pota" is an onomatopoeia / sound effect referring to the sound of something dripping. In this case, it's SFX of her sweat dripping.