Can you help me find this isekai/western? romance manhwa ;-;

I don't remember the story 100% but it's sorta like this

FL is neglected by her mother who only loves FL's sister.
Idk if FL's sister suddenly returned to the house, but FL's role in the house was to give up everything to her sis. (kinda like the real daughter is back but not the same)

FL's mom tried to set up FL's fiancee (ML) with FL's sis, but sis is a normal and understanding character who gets that ML likes FL and wants FL to be happy.

But ofc, FL has a ridiculous misunderstanding when sis and ML are talking to each other when her sis falls sick. Whether or not FL is a reincarnated character who knows the story is unclear to me, but she thinks ML would be better off with her sis.

ML and his mom are blonde.
FL saved ML's mom from falling into a lake when she was younger, and ML's mom always wanted to adopt the neglected FL. ML and FL met each other when they were kids
I think FL can talk to fairies or smt idk exactly.

At a later point in the story, FL's mom takes both sisters to meet the empress, but FL's sis is not as mature and sophisticated as FL (I think idk)

I"m being hella vague, but I'll be eternally grateful for your help uwu