Comment by Mero cat khoi on I Became the Contract Daughter of the soon-to-be-ruined Family - Chapter 31

 so the MC (let's call her Annette or Ann from now on) is a soul that came from Korea to land in the body of her current host, who actually is the daughter that the Duke of Aubrey had lost. the reason why the eyes became a different color is pretty complicated but the short of it was that the Demon of the Void (DoV) had taken the color along with the power of rust from the body when the original soul made a wish to it. The OG soul or Annette (we'll call her Shekina for now) is the other green hair purple eyed girl in the pictures in the first post; she became the current DoV due to that wish she had made in her past life. her past life being the one that is the story that Ann is recalling.
The end of the main story has Ann and the Aubrey family living together along with Shekina. Duke of aubrey learns what's going on with with Ann (her body, soul, and shekina's situation both present and past) around the latter half of the story.
Silver haire ML is essentially dating Ann and in the last SS Ann finally accepts being engaged to him after kissing him to see if she really does like him. The other SS just shows the Aubrey family going on a family trip to a private island and announcing that Shekina would be officially part of the duke family as the older sister    (FOUND THIS IN NOVEL FORUM, written by KAGERYUU)