Vera knew the matters belonging to factions were complicated, and although she understood how desperate they were that they even needed to sneak people up the realms to try and come up with some kind of solution, her interest still comes first. No matter how much empathy a demon felt, their desire would always come first, lest they would not be considered a demon anymore.
"I don't know what the details are, but I really couldn't give up descending the realm. So your choice would either let us pass through peacefully or finish what we have going on right now and we let us pass through ourselves."
Of course, just as how the scrawny humanoid demon didn't back down earlier after Blake's refusal of his proposal, he also didn't back down after hearing Vera's statement.