"You taught me everything I knew, Erik. You were my truest friend. Until the day you returned and you weren't."

The implicit trust that had started with acceptance and romantic sentiments in the mansion and evolved over the years had been so completely betrayed when he attempted to kill her, exposing her existence to the world, and sending the shapeshifter fleeing for her life while her world was reeling.

The fresh hurt and confusion was still there, lingering in her blue pools of her eyes, but so too blackest depths of her ferocious anger and grief from other events that such a betrayal had compounded. That had made the missed opportunity to kill Trask at the Paris summit all the more agonizing and costly to Mystique.