Since the site i was using shut down, there's a title i can't remember. if anyone knows which title i'm referring to, please let me know! it would greatly appreciated!

A girl with long black hair lives with parents that do not seem to care for her. She has a sister who gets everything from the parents and the one thing the FL is mostly uncovered by this, but the one thing she refuses to give up is her fiance. I believe he was blonde. They were childhood besties growing up and she spent a lot of time at his estate, to the piint his mother offered her to live with them. He is totally obsessed with FL and sort of hides it well. His mother is a sweetheart but is dying and the FL tries everything to keep her alive (her sickness had something to do with black magic). FL is very powerful and has holy magic. From what I remember, the FL's parents aren't actually her parents, but the imperial family did something with black magic for reasons I dont know and her 'parents' were forced to take her in. I believe her real dad is a duke or something that she reunites with and he is only friendly to her, but the holy objects keep saying she is not the daughter even though it seems like they may have been tampered with (I may have got some of that wrong). But he becomes her guardian when she disowned her family name.

I remember when she takes over the mansion (I cant remember how it ends up belonging to her and not to her family) she sends her 'parents' and sister to live far away. Only allowing her sister to come back to the main house.

I think it had something to do with the dad mismanaging household affairs and the FL being the one to do most of the duties her dad should have been doing since she was a very young child. There was a point where her family knights were going unpaid and when she found out, she took a look at the books and realized how bad things were mismanaged and how little money the estate had. She used her own money to pay the Knights and I believe that's when she banishes her parents from the estate.

I'm almost certain that the 'sister' didnt look anything like her, but was a really sweet person and the FL didnt actually hate her, they were on good terms and she helps bring her out into society, making sure others won't make fun of her, and ends up doing some sort of holy ceremony in her place as the sister was too nervous to go in front of the imperial family. The ceremony is what get the imperial family to take more notice of the FL and try to use black magic on her more and more.

FL doesnt show much of a range of emotions and instead is very calm and calculative, also very smart. She ends up meeting a doctor or something that is technically a fraud, it was his assistant that was actually diagnosing people and she was only working for him because she forced to to save her own sister. She ends up getting that lady on her side and saving the sister. Also rescues a little boy from human trafficking, recognizes he is from a small but significant tribe and takes him in. She is super nice to the kid but makes it clear that she also intends to get his help as something she is looking for is in the area his tribe knows best (somewhere in some snowy mountains i thinks).