Well from the little information i knows about HALO and from reading almost all of the HALO Novels...from what i reads and heards, there are 2 (Two) possible ways she coulds be saved.
1s) There are more than 1 composer and she is turned into human (which I hope will happens)
or
2s) Chief miraculously finds cortana somehow and converts her into a Forerunner A.I. (aka Ancilla) with the help of Mendicant Bias. (another way which is kinda ok with me)
**SPOILER** Ohs ands i hope Chief finds out that Parisa, Chiefs Childhoods friend that he met somwhers inbetweens Two missions of HALO 2 is alive
MasterChief-117