Cassandra-075

Cassandra is, as of yet, a mysterious person in the "Halo-verse". She does seem to know the Master Chief, considering how she knows his number and his real name, but the fact that she calls him "John" while the other Spartan II's call him "Squad Leader" would lead one to conclude that she might not be an actual Spartan.

There is also the fact that "Cassandra" is 9 letters long, while the majority of the Spartan II's have names that are either equal to or less than 7 letters, though Cassie is a possibility, as William is Will.

For the time being, Cassandra is residing in the confines of the M25L Recovery Station, undergoing a myriad of recovery procedures.

Cassandra is possibly the young girl with the young John-117 on the Planet Reach in the Starry Night Halo 3 Trailer; the other two primary Spartan females - Kelly and Linda - Have Blue and Crimson hair, respectively.

From Conversations from the Universe:
117

As you might imagine - though I know you won't - I've heard quite a bit of your recent adventures on the Halo. I'm glad you made it; I have to assume you always will. Recovery is going well and I am proceeding on to fourth-stage rehabilitation. It is significantly more painful than previous stages, but I'm happy to be skinned once again.

I hear that you will be testing the new Mark VI. I will definitely look for the reports on how it works out. The specs are obviously improved, but the choice to incorporate further Covenant technology somehow makes my skin crawl.

We miss you, John. I've asked Sergeant Johnson to let me know if you're ever near the M25L Recovery Station and perhaps I'll be able to come see you. I'm hoping I'll have the chance soon. Today, humanity feels pale and thin with only ghosts to defend her heart. I feel much the same.

I'll write again.

-Cassandra