It's not that hard to follow. Her mother was imprisoned in that country, as they took her item of power or whatever. The daughter was raised to marry the prince to get those sweet, sweet dragon genes in the royal family. When the daughter found out about the engagement she immediately said that "she don't want no Scrubs", pulled a Saiki K, and made the whole country appear beautiful.
Along the way, she freed Dragon... Step.. Bro? ahem, and, uh, fell in love with him? Possibly not related! Could be adopted! It's Medieval Era Japan Style, moving on! She would have went with him then, but she was probably bound by her or her mom's word to marry the twerp prince, so she had to suffer with that until he either died of old age (dragons can live a helluva long time, you know?), or he did something stupid like break the engagement. Luckily, his infatuation with the kingdom's donkey made him do the latter, and now she can get with Dragon stud with her full power intact. She also removed the geass that made everyone look like super models, and left the bumpkin girl to her scrub prince. The End.
........ "What are you doing, Step Dragon Bro??" (Sorry, I had to.)