A drama where FL ends up with the guy with whom she was "not destined" to be with.
here me out. it has nothing to do with ML or SML. the Guy can be ML SML TML i don't care. but the theme should be like this :
 Guy 1 and FL are meant to be together, as in soulmates.
 soulmates can work in any manner. Maybe they were long lost lovers. they represent the power couple. maybe something  like nisekoi where guy1 and fl had promised to marry when they grow up and then it was a struggle to find guy1 once theyre grown up. or maybe in a fantasy setting where Guy1 and FL are link through many lives they have spend together and they again cross path in current life. something like star crossed lovers. or maybe like in witch's love where Guy1 is supposed to be FL's lifeline vice versa. or maybe someone FL had fallen for years and years ago and was searching him and finally found him. or something like they're bound by the red thread they are soulmates like in the vampire diaries. maybe some form of imprinting anything. one true love.

But FL does NOT end up with Guy1 but with Guy2 instead who has no such connection with her. Role reversed is also okay where ML is soulmates with Girl1 but ends up with Girl2. 

is there any drama like that? please help me out, im stuck with this kind of scenario in my head.

some dramas that are like that,
ones that i have already stated
nisekoi : ml had promised to marry sfl when they where kids. and they had made the promise in a lock and key toy. he had the lock and she had the key. fast forward highshool ml and fl have to pretend to date to please their respective mafia families. ml doesn't know sfl is his promised girl but is madly in love with sfl. sfl is also crazy about ml not knowing they are their childhood loves. fl starts falling for ml. sfl and ml never confess. ml falls out of love for sfl and falls for fl. and even when he does find out his life long crush was his childhood promised girl he still dated and married fl

witch's love : fl is from a family of witches. fl's life can be made safe if she remains close to her destined lover sml. the magical soulmate. yet falls for ml and goes against everyone to be with ml

TVD: i think everyone already knows vampire diaries but maybe not the book. in the book elena and stefan were considered soulmates like the actual meaning wise not out of respect yet she chose damon

my ambulance: not so much like the other three but fl and ml were magically linked by love. ml could teleport wherever fl was if she called him. and this power was exclusive to them. their relationship goes haywire when 15 years later ml is too much obsessed with work and barely gives fl time or care but he still loves her deeply.  suddenly a much younger colleague of ml and fl gets the ability of teleportation as well. out of blue. and fl has never seen him. she decides to stay with sml after the entire content of the series

Itaewon Class - that fits this well. Really bothered me a lot that they used this theme here XD

Also what you may also like is Lost Romance. The story is quite well known, girl ends up being thrown into her novel and ends up being the villain. But she tries to change the outcome and help the main character and her love interest. But things are not working out in her favor, since she is the villain after all. 

  • Love Alarm/Love Alarm 2- FL's soulmate was determined by an app but in the second season she choses to not follow that destiny in the end
  • Love Between Fairy and Devil- FL was engaged toto her crush  SML without knowing. She was meant to fulfil her destiny to protect her world  but she fell in love with someone else.

My Roommate is a Gumiho - A good bit of the dramatic tension in this drama centers around the question of whether the red thread/string/cord of fate that ties two souls together is unbreakable, or can be cut.