You might be referring to "The One Within The Villainess," a black and white manga set in a school, but I'm uncertain about the details of pink hair and pigtails.
It isn't that one, but looks like a fun read !
Not exactly the same but maybe: https://www.mangago.zone/read-manga/i_don_t_care_let_me_go_home/
I LOVE YOU SO MUCH （/TДT)/
It isn't the exact same one, but close enough! I've been wanting to reread this as well (๑•ㅂ•)و✧
I have been looking for this manga for over 1 year... I CAN'T FIND IT.
(Honestly, it might've been a daydream or dream I had about a manga and I'm mixing it up, but..)
So the story plot is something about a girl in Highschool, she has pink (or maybe another colour idk) pigtails and studies. She is in a world of an otome/manga, but she isn't reincarnated and knows absolutely nothing.
I don't remember much, but I do remember there was a scene where the og FL blamed Pink-Pigtails for pushing her down the stairs (she had short blonde hair), but then was proven wrong from the og ML. (?)
More explanation: Pink-Pigtails was holding books and walking down the stairs, and then when she reached the bottom step, Blonde-Bitch rolled down and being dramatic. She then accused Pink-Pigtails of pushing her.
Details: Black and White manga. Newer manga. School/Academy setting
PLEASE HELP ME FIND THIS GODDAMN MANGA I JUST WANNA SEE THE NEW UPDATES