- last post: 01.01.0001 12:00 AM PDT
Good question.
Cortana has already betrayed. She knows just as well as the Chief or anyone in the UNSC that she must not fall into the enemy's hands for they would gain access to every defense the UNSC has, including the location of Earth. The Covenant are the least worrisome, since they already know where Earth is. The biggest threat now is the Flood, of which they along with the hive-mind, has escaped Halo with access to High Charity. She should've carried out her duty by destroying High Charity, the Flood, Halo, as well as herself for the sake of mankind after MC made it to safety. But she didn't. In no way can she miss Halo preparing to fire. Had it not been for the Arbiter, Johnson, and Miranda.. Which leads to believe that Cortana willingly remained on High Charity(it has been considered that Cortana need not to be within High Charity to detonate In Amber Clad). What more, she allowed herself to Gravemind's presence.