Looking for red hair fl webtoon

Transmigration. She went into a villainess' body with red hair. I think she was poisoned? She coughs blood and stamina drains whenever she takes a few steps. Hmmm the artist often make her look like a fish I think? Also there's a slave who acts really close to her but real suspicious. End game is a white haired duke I think..
If you remember the title please share ty
ヾ(❀╹◡╹)ﾉ~