This maybe so far off, but what if... spoilers..

What if cortana is the librarian…
I know… crazy.
But…
Halsey is smart… very, very smart. She knows a vast amount of info on forerunners. What if hasley was imprinted with the librarian.
Then halseys bra in was used to makeep cortana. Making cortana also the librarian.
This could explain why chief and cortana have such a loving relationship. Chiefs imprint is the iso didact. This could also explain why Cortana is bringing up all of these guardians to “protect” all the galaxies beings. This could by why she locking her “love”, chief, or the iso didact, in a cryptum while she does this.
Idk. It’s friggin nuts, but cortana seems to be doing everything the librarian did.
Hell, even the librarian said the cortana wasn’t a normal ai.
I mean… what if?!