There's a pecking order in the rinks with every coach and especially the top ones like Raf. His priorities are Chen, Wagner and Rippon right now. Raf also coaches Brezina, Ponsart and then of course Mariah. So the latter two are less of a priority right now than the first 3-4 skaters. All coaches do this, you'll work with an assistant coach more if you aren't one of the priority skaters at the time. For instance, this happened to Lysacek when he went to Carroll in 2003. He worked more with Congemi with Carroll's orders due to Frank having more prioritized skaters at the time such as Goebel.
So in Mariah's case her choice is not to work with Rohene in CO when she doesn't get priority time from Raf in CA right now etc. That is definitely not how these things work.