The situation was beginning to clear up.
Sisi's faction was of the opinion "against rebellion," or rather, unwilling to fulfill others' ambitions to consolidate the Miao Region. Their assassination of the Provincial Governor was not an act of rebellion, but rather the opposite—it was to extinguish others' excuses for rebellion.
Since the Xia oppressor had been assassinated, it would be difficult for you to rebel using that as a reason.
Moreover, the assassin was Yue Hongling, a Xia person herself. Xia killing Xia, what does that have to do with us? Even if the Imperial authorities pursued the matter, we could remain uninvolved.
Under normal circumstances, Sisi's idea might have seemed somewhat naive—if they really came to hold someone accountable, wouldn't the local area still be plowed through? But the current situation was somewhat different...