It could be. If Sarah faced some sort of supernatural or terrifying situation in the basement like encountering ghosts or a deranged intruder, then it would be a horror story.
Once upon a time, Sarah was walking alone in the old cemetery at midnight. The moon was hidden by dark clouds. As she passed a mausoleum, she heard a faint scratching sound from inside. Her heart raced as she saw a pale hand reaching out from the cracked door. Without thinking, she ran. But every step she took, she could feel cold breath on her neck. Suddenly, she tripped over a fallen tombstone and when she looked up, a shadowy figure was looming over her.
Imagine Sarah in an old attic. She's looking through some dusty boxes when she finds a locked diary. As she tries to open it, a cold wind blows through the attic. The candles she had lit go out. When she relights them, she sees a figure standing in the corner. It's a little girl with a sad expression. But as Sarah approaches, the girl's face twists into a menacing scowl and she starts to float towards Sarah, moaning.
Well, it depends on the reader. Some people are more sensitive to horror elements, so for them, Sarah's horror novel could be extremely terrifying. It could have things like dark secrets being revealed gradually, and a sense of impending doom throughout the story. But others who are more used to horror might not find it as scary.
Sarah was significant as she was Abraham's wife. She was part of God's plan to create a great nation. Even though she was barren for a long time, her eventual pregnancy and the birth of Isaac were important steps in fulfilling God's covenant with Abraham.
I'm not sure exactly who Sarah is without more information from the story. But she is likely a person who has a weight problem and is the focus of the '600 pound life' story.