I think this is the manwha https://www.mangago.me/read-manga/the_real_daughter_is_back/
unfortunately this is not the one... thank you for the recc though!
honestly im almost lead to believe that i dreamt this manhwa up...
Noo I vaguely remember this, I'll find it and send it
https://www.mangago.me/read-manga/there_is_no_place_for_fakes/
Is it this dawg?
yess!!! thank you so much! woof!
Your description was very detailed and helpful ( ◜‿◝ )♡ Have fun reading!!
not sure if this cuts it down or anything but...
the mc, the villainess, as a bratty child read a book that was about the main protagonist, and finds out that her life ends with death (its not reincarnation or issekai)
so to change her future, she fixes her personality in favour of her father (who was the one that ordered her to be killed). she isnt the real daughter of her father, so she tries to find her so that she can leave and have a peaceful life.
she finds the actual daughter in some commoner village and also finds out that her mother swapped her was she was a baby which is why shes not the real daughter?
she has a childhood friend, who was told to be friendly towards her, she had a crush on him until she read the book
another male character is the pppprince?? or something and she was alone when he approached her, he was supposed to end up with the real protag but he ended up falling for the villainess.
its kind of a lot and may not be very specific, but thank you!
tldr;
reads a book about her future, finds out shes the villainess and not the real daughter so she goes to find the real daughter to live a peaceful life