I think her former country was meant on the doom road anyway without the MC's intervention. She is a commoner turned knight (like Yi Sun Shin) and when she is already in command, no one from the aristocrats wants to stay anymore (during YSS time Gwanghaegun stayed so they won) to support ( I think most already fled) - this is the same . When you loose your backing its over.
yeahh i guess that couldve been the situation, since shes is a commoner AND woman whos a commander it makes sense they'll feel like that but it still sucks because it showed that everything that they worked and fought for, their country they sacrificed for was just doomed by a traitor and surrender, kinda deafeated the purpose of their struggle in war dont ya think, estelle and her co-knight buddies had a pretty bomb relationship and now theyre out for revenge ah the bloodlust aHHHhh~ well i can rant about it for ages but the point is, its enraging getting betrayed by your bff then reincarnated into the body in a country that you fought against and lost to TTvTT, and that scene when she was so close to the king gOSHHHH she was so close to the person she tried to kill for years ;-;
ayoyo u should totally get back with your co-knight buddies and yaknow burn that fucking kingdom to the ground :) no one there deserves salvation <33 specially that white haired freak ♡ so yeah just fuck the romance and lets go straight to the genocide yeah? love u (づ ̄ ³ ̄)づ