AHHHHH

firstly, beware of the villainess also made me so mad like I liked the ml but the og fl was def the better option

secondly, there's unfortunately not a lot of isekai/reincarnation manhwa in which the fl ends up with a girl (there's lots of historical/fantasy ones tho) but here's a few ik. I've added some manga too x:
https://www.mangago.zone/read-manga/the_fed_up_office_lady_wants_to_serve_the_villainess/
https://www.mangago.zone/read-manga/i_favor_the_villainess/
https://www.mangago.zone/read-manga/please_bully_me_miss_villainess/
https://www.mangago.zone/read-manga/after_transmigrating_into_a_book_i_snatched_the_role_of_the_male_lead/
https://www.mangago.zone/read-manga/the_daughter_of_evil_and_miss_devil/

this one isn't isekai but it's set in a fantasy world and it's rlly rlly good:
https://www.mangago.zone/read-manga/do_you_think_someone_like_you_could_defeat_the_demon_lord/

this one also isn't isekai, but historical and it's between the maid and the lady of the house, it's smut tho:
https://www.mangago.zone/read-manga/marie_and_alex/

Omggg thank you so much. I hope you get railed

https://www.mangago.zone/read-manga/the_pet_of_the_villainess/
She doesn't end up w the og fl. Instead there's this kinda love triangle between mc, fl and mc's predestined partner, which is such a good.
Mc and fl are very close and at times are very much Lovely dovey and professing their unconditonal love for each other...so kinda gay
This is a manhwa that calls out the mysoginist shit that ml put the fl through

I hope you get railed it's insane to say but i kinda love it