Towards the end, the MC makes a huge mistake. In addition to almost losing her life, she endangers her brother's throne.

Theres two scenarios I'm thinking this might refer too. 1) they're referring to when the FL got attacked and had to leave the city then fight a civil war with her uncle because he was rebelling. Idk why they think this is a mistake on FL's part since she had no idea it was coming at all. First, the initial attack came from her Uncle-in-law, who she was close with since this was her full blooded aunt's husband. Second, the third uncle was the one who plotted to overthrow her and her brother. This third uncle was also close to her and literally watched her grow up. He used to take care of her too. Because she never expected the attack to come from two of her closest relatives, idk how you can call this a mistake. She would've died if she didn't leave. They had the palace and city surrounded and her maid had to disguise as her so that FL could escape. 2) They're referring to when FL was traveling to a monastery to pray for the people since there had been a lot of snow lately and there was some disasters because of it. She gets attacked and falls off a cliff. Again idk how this was FL's fault since again, the attack came from a trusted person, her personal maid who had been with her for a decade +. Plus, she knew the attack was coming. She just didn't know who was going to be the one pulling the trigger, her great-grandma or her step-grandma. The trip was only to lure them out and get them to attack her since she needed a chance to finally do something. After the attack, she uses the chance to get rid of alot of their cronies in the administration so that it was easier for her brother to rule. Another indication that she had planned this was when she was found by her personal guard about 1 day after she fell off the cliff. She was only injured because she wasn't expecting the attack from her personal maid.

ML has a BF/rival from school who he competes with. Granted the competition is more from Bai Jiayi's side to beat the ML in something. There's a line at the end that the ML says, "Finally, Bai Jiayi, the political and love rival, was completely resolved." This kinda came out of nowhere for me. Probably because this was MTL but I couldn't pin point where Bai Jiayi "fell in love" with FL. Honestly, he kinda disappears from the plot for periods of time until he was needed and then he shows up

there's a couple of notable examples. There's the two I mentioned in my response to MsEliteNeet's spoiler and another notable one is from her own mother. Her mother gets suspicious toward the end that FL wanted the throne for herself and wasn't going to return it to her brother. It's not mentioned but it's implied that there's been people who have been whispering things to her about this. Her mother had always dismissed it because FL was fighting to get rid of rivals to her brother's rule. This was further exacerbated by the fact that FL mentioned to her mother that she wanted to marry ML (because her mother was also pushing her to get married now that things had settled down), who is a pretty prominent person at court at this point. FL asks why and her mother's response was that they were both to headstrong to workout with each other. They both needed someone "gentle and understanding" to balance it out. IMO this was a lie that the mom was telling herself. I think the real reason why is because if they get married, they would be too powerful as a couple for the mom to do anything about. She didn't reject her daughter becoming regent because she knew she was too weak to handle the job