Plot: MC's real mother is a maid, who had an affair with the duke, swaps MC with the original heir and runs away. The duchess is completely obsessed with recovering her real daughter and always abuses MC. But MC still works hard to become the perfect daughter. Finally, after the maid dies, the real daughter returns to the family. Now, the duchess wants to secretly swap the daughters, and let the real daughter assume the identity of MC, as the real daughter with superior bloodline should be way more capable than MC. MC decides to ruin this family for taking away all her work andeven her identity.

Review
For first 20 chapters, MC pretends to be a badass Villainess while bullying her innocent sister. Then, MC just runs away to a faraway island for a cute slice-of-life story running a shop for 50+ chapters. The "revenge" is just ignoring her family as they fall into ruin by their own incompetence. Author probably ran out of ideas after first 20 chapters and just kept adding random plotlines to keep the story going.

MC is definitely author's self-insert. She is perfect. She can do no wrong, while all her enemies are wrong. Most of the powerful characters belong to her fanclub. Every other character is defined by their relationship to her and other characters exist to validate MC or feel bad about MC's tragic childhood abuse.
Everyone's always praising her for being super smart, strong etc. and despite that, we rarely see even a hint of that intelligence on screen. The story of her sister turning into a badass knight was way more intriguing and she definitely should have been the lead.

For a story that deals with illegitimate birth of MC, it instead chooses to double down on special bloodlines and how you can inherit cool magical powers by being born to the right parents. The whole magic thing is completely nonsensical and just becomes whatever the plot needs.

This is a second-rate series carried by art. If you are starting this series, just remember that the first 20 chapters are tonally *very* different from the rest of the series.