I hate their Halo 4 relationship. It's not badly told, Don't me wrong.
The thing is, i though the handling of the relationship between chief and cortana in halo 4 was pretty good, but the context that it all occurred in was.... bad.
But Cheif and Cortana have known each other for less than 3 months and have actively worked together for less than a week by the end of Halo 3.... Their sudden closeness in Halo 4 makes zero sense. Halo CE-3 they seem like colleagues who get on well, not best friends.