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Doesn't the main player character defect because the Empire starts to burn her homeworld to the ground, despite (or even because) of its devout loyalty to the Empire?
Operation: Cinder was about devastating the Galaxy, including loyal Imperial worlds, so that the next government was left with little to rule (and because, to quote Palpatine in the last Aftermath novel, an Empire incapable of protecting its ruler does not deserve to survive after his death).
I can see why someone would abandon their government if that government (to which they had been loyal their entire life) seemed to spontaneously turn on them.
Or did I miss something?