The teenage girl at the center of the prep school rape trial testified this week that she worried about offending her alleged rapist, a popular senior student at St. Paul’s School, even as he “scraped” the inside of her body, bit her, and spat on her during their alleged encounter in the school’s mechanical room.

Nineteen-year-old Owen Labrie, a former prefect at the elite St. Paul’s School in Concord, New Hampshire, stands accused of raping a 15-year-old student in 2014 as part of the school’s unofficial, traditional sex competition where senior men try to sleep with as many underclassmen as possible. Labrie’s defense,…