I'm just working your possibilities. The Founders must place AM one and a quarter steps below G and half a step above the forces now threatening them. They have AM's staff, and could even threaten to destroy it. (Does Jaylene know what that staff is?) (Aside: do the spears itch in Alda's hand? I'm thinking of Anver's demo with the other mage's/student's staff.)
You've built a tremendous point of conflict here, one that could shake Jaylene in the crisis moment, threaten all the resolve she's built up--especially if Alda was somehow part of how that resolve was built up.
And what if Jaylene makes the wrong choice, but is too late to stop Alda, and has to watch as Alda's actions rally the enemy--right before she destroys the Horrors.
The first law of battle is that the enemy changes the plan. What if the only hope of ending the battle is to destroy the Horrors so the enemy will have nothing to fight for, and AM is the one who understands it?
And this leads to a possible redefinition of the Alda/Jaylene relationship. By their presence and character they constantly test each other. By right of power, Jaylene should be the tail in the dog, but Alda wants to be that tail. She keeps pushing the role of war dog on Jaylene.