Cortana: The Best AI in the UNSC

Cortana was the best. Without her guidance, Master Chief may have never defeated the Flood. After destroying the Composer, she was lost. The UNSC will miss the one AI that stood up to the Gravemind, the one that warned us about Halo and its capabilities. But, the one who will miss her the most is the Master Chief. Does Dr. Halsey have a solution? Partial AU after Halo 4 events.