Okay, having binged this over the past day, I'd like to say something, and lay down my vote.
Mosi is still Amani's sister. On some level, they still care about each other, or at least want to care about each other.
However, Mosi is quite fucked up as a person. Judging from her remembering her academy days during and after the war, Mosi is dealing with abuse from her teachers and peers, as well as (maybe, just speculation on my part) resentment over her mother and sister seemingly abandoning her. That's not even getting into whatever indoctrination the Holy Imperials put her through during training.
All this doesn't excuse Mosi shooting Anja. Even if she's arresting you, you don't just shoot your sister's best friend. What this does mean, especially given Mosi's surprise that the Saturnian Imperials aren't complete dicks, means there's a good chance we can get all the Norths on the same side of the war.
I'm afraid that if we vote for feeling betrayal, redeeming Mosi will that much harder. Probably won't be impossible, but it will be harder. Ergo, I'mma vote for:
[X] Fear and existential dread over everything going wrong in an escalating war