beta
I went on to read it elsewhere (had points from plaza) and here are some spoilers for y'all.
1. The prince bought her the first night because he thought it was, in fact, his ex-fiancée and wanted to be sure. Them having sex was after he got carried away.
2. It was common practice to go to a brothel to get experience. It was true his uncle told him to go, coincidental that he went to that particular one she was sold at, but intentional that he bought her.
3. They both fell in love with each other, him knowing that it was her and hiding his identity, her just falling for him and thinking he looked familiar (chapt 13 she finds out after he falls asleep next to her).
4. The one who sold her was the trash girl, not her father. Her father lost sleep trying to find her and appeal the annulment of the engagement.
5. The prince never allowed anyone else to buy her and when she tried to cut him off, he bought the brothel. It worked in his favor when he was trying to re-establish her position as crown princess. Convinced the nobles that she was untouched because he saved her in time (in truth, he was the one who touched her... Repeatedly).
6. Trash girl gets exiled after everything comes to light. Looks like she's planning on doing something else later on but that's the latest chapter. After she sold the FL, she heard news that the FL was stabbed to death by a customer, so she thought she was in the clear for being crown princess. The prince hired someone to lie to her, so she thought he was going to the brothel for experience for their wedding night.