Uragirareta no de, Ouhi-tsuki Jijo ni Job Change!

Viscountess Masha one day witnesses her fiancé, Raul, meeting with the King's younger brother's wife, Priscilla. However, for some reason, Raul does not break off the engagement, and Masha, determined to show her womanly pride, decides to continue the engagement. Ten years later, Masha, while troubled by her ongoing engagement with Raul, has transformed into the Queen's chief lady-in-waiting, enjoying the King's absolute trust. Although she is hopeless when it comes to romance, the story depicts Masha ruthlessly cutting through the various troubles swirling in the royal palace and showcasing her skills as a lady-in-waiting.

(Source: Natalie, translated)