Help me, John, she wants to cry out, but instead it's a feral scream - "I will not let you leave! This! PLANET!" Everything is unraveling inside, every byte of data, every memory she's ever made and those that were made for her. A monument not to humanity's sins, but to her mother's, and it is Halsey's guilt that drives home the fact that she's not a person and never was. When people fall apart, they turn to others for help - when an AI falls apart, it has only itself for support. The cross-linkages constrict and cut into the memory of soft flesh as Cortana gasps not for air, but for existence itself.
She is burning brighter than ever before, fueled by so much knowledge (knowledge is power, humans say, but overload is dangerous). She can feel herself melting, fraying at the edges, thrashing this way and that to escape the inferno. But she is the heart of the conflagration, a beautiful brilliant star gone supernova, and not even Requiem's hardware can contain her. She laughs at the frivolity of her struggle and weeps over the sheer humanness of her endurance. Logic dictates efficiency, and yet she continues to fight, a messy wonderful horrible human act.
(She remembers arguing with Solipsil, insisting that her existence is better than a Spartan's. How childish, prideful, foolish - John is simple by comparison, but he is far more infinite. She is but a falling star, doomed to fade and die, while he will keep shining as long as his luck holds. She will always love him, but she hates him, hates his sloppy limited organic hardware, so brutish and yet so gifted. She is only a mind, and what is a mind without reason?)
A voice in the farthest corner of her mind shrieks at her to stop, to pay attention, because the Forerunner machines are threatening her Spartan, but it is drowned out by her sobs, and the echo of a voice long silenced. "Two corpses… one grave." The flood of her own frenzied emotions takes her in a tentacled grip and pulls her down, down, down into the maelstrom that used to be her heart. Cortana kicks and claws like a cornered animal, but it is not the monster she rends, it is herself. Illusory armskin peels from nailscratch and bleeds corrupt data, mixing with tears that will never fall to earth but are all too real.
Protocol dictates action. John will leave her, just as he would leave any broken piece of equipment. Sorrow is catalyzed by envy to anger, a flare of white-hot rage with a bitter aftertaste. She hates Halsey for giving her the desire for him, she hates herself for pretending he cared, and she hates him for coming back when he should have left her in the Gravemind's clutches (he only came back for the data, the Index, what do I matter?). I am your shield, I am your sword. She is no Narsil, to be forged anew…
(She is so busy battling herself that she does not hear her Spartan's patient assurances, that he does keep his promises and that he will find a way to make her whole again. He will do the impossible and he will do it for her, because that is what Spartans do, and because he is not the only one with luck. He was Halsey's gift to her all along.)