It's like https://www.mangago.zone/read-manga/housekeeper_in_a_dungeon/
But more dark and angsty, female lead is the only one compatible with male lead, she dies and gets sent to the past which is the original timeline of the male lead who died Bec she did?? He ends up finding her again and becomes obsessed??? I believe past live fml has brown hair and her new life (diff timeline) has pink hair LMK ASAP IF YOU GUYS KNOW IT
MIAE, CMON NOW.... YPU BETTTAAHHH NOT pull a "oh I actually like this guy instead" or a "it was just me playing around" girl cuz imma tweak out