If there's one thing that will make Jang Ok Jung fight is when her mother is being hurt, trampled upon and disgraced by the nobles of the society, in this instance the Queen Mother and In Hyun.
Ever since she was a child, she stood up against oppression. She would willingly replaced her mother being punished by her lords/masters.
But now, she faced both the Queens. And without a thought slapped the Queeen's court maid. Her audacity made the Queen realize Ok Jung's character of that of a fighter.
The episode continues with the romance between Ok Jung and King Suk Jong aka Lee Soon. He can't stop himself from going to Ok Jung whenever she is around even if he is busy. He is very attentive to her.
And of course the love and affection soon made Ok Jung anticipate a child. She is pregnant. [as I understood :)) still have to watch with sub ]
But an unfortunate accident made her fell off the horse. She is crying so hard. Lee Soon heard her anguish through the door. He felt her pain.
The ending scene, he told her he'd appoint her as Hee Bin. [this i definitely heard :)) ]
And Ok Jung is crying with happiness, while Queen In Hyun witnessed the whole scene.