Kahlil says nothing to counter Rhy's argument - though he himself plans to share this with the other delegates, in exchange for information their own negotiations. But he would not be doing so if he expected the information to immediately be brought to opposing faction leaderships. More than likely, spycraft will uncover what deal Thorne has made - they share the bay with Solvunn, after all.

But -

"It's as Rhy says. Thorne can't and won't take responsibility for another faction in these dealings. But, maybe you can trust that no faction can afford to make more enemies."

It was never a guarantee to begin with that all three factions would come to the table - one faction reneging doesn't necessarily mean the Nether will fall, even if it lowers the odds of success. And that would put whoever did at a disadvantage as far as the balance of future scales in the conflict, should the Draconae recover.