ISO specific manhwa

omg I just read this the other day but I can’t even remember what it’s called- all I remember is that 2 horses fall in love and that brings the two MCs together. The horses name was like Marilyn I think? And the FLs stepsister is a bit chubby and has a relationship with some blonde guy she dances with at the ball but never forgets to get his name. IF YOU KNOW PLEASE TELL ME!