This one may be a bit obscure, but I once read a book as a child (Young Adult, Fiction) where the main character is a teenage girl who lives in the country on a farm or ranch in the middle of nowhere with her father and siblings. She is afraid of horses, particularly one - a horse her mother rode and fell off of and died. Her father eventually hires a farmhand who seems odd, and as the book progresses, the girl looks into the farmhand's past and meets his mother (Opal/Alma?) who reveals that the farmhand is a killer or some other kind of antagonist. At the end the girl is left alone at home and ends up having to ride the horse to safety to get away from the farmhand. Does anyone have any idea what the title/author of this book may be? Any help would be much appeciated.