OK , I'm gonna make a unpopular opinion , Renner did nothing wrong. With how stupid the nobles of the Kingdom was, the kingdom was going to fall sooner or later (the empire was already wearing down the kingdom with the yearly wars in preparation for a eventual conquest). Renner did what she had to , to secure her own happiness by siding with the people she knew were going to win(a bunch of the stupid nobles that had pushed for war tried to do the same at the last minute by killing the crown prince). She never had any loyalty to the kingdom to start with, because to the kingdom she was nothing but a tool to be used or sacrificed.
Basically , much like Han Solo , Renner shot first.