Harper Essex-Pembroke is a student at Princeton University and the head of one of the exclusive Eating Clubs. She and Spencer Hastings are initially quite friendly but end up being enemies by the end of "Stunning."
Harper has blond hair and wide violet eyes.
Harper meets Spencer at a dinner for Princeton's early-admitted students. Since she is a student ambassador, it is her job to assist and welcome the future students. She instantly warms up to Spencer and invites her to the Ivy House on Princeton's campus. Harper is the Bicker Chair of Ivy Eating Club. Eating Clubs are secret societies that are coed and provide members with a plethora of networking opportunities. Thrilled to have a chance at membership to this exclusive society, Spencer accepts.
At the Ivy House, Harper introduces Spencer to the other members and invites her to a party on campus for the night. At the party, Spencer notices the girl smoking pot outside and gets nervous. A while later, cops break into the party and arrest Harper. Since Spencer was the only girl who saw her smoking, she instantly accuses her of telling the police. Spencer vehemently denies any involvement, knowing that "A" must have seen them and set her up. She is kicked out of the Ivy House and must stay at a cheap motel.
Spencer apologizes to Harper several times and insists on her innocence. She tells the college student that she's had her own struggles with drugs in the past and wanted to keep a low profile. Harper hesitantly accepts this and invites Spencer to a potluck gathering on the condition that she brings food. Spencer somehow interprets this as instructions to bring a dish with pot in it. After begging the motel manager to use the kitchen, Spencer comes up with a dish. She arrives at the potluck with several trays of brownies baked with pot.
The party becomes wild as everyone partakes in the brownies and Spencer tells Harper that she put pot in them. Harper is surprised but amused and delighted, which in turn shocks the high school student. However, little does Spencer know that A spiked her brownies while they were baking. Spencer fell asleep while the brownies were baking, giving A the perfect opportunity to add LSD and Ritalin. Harper ends up on academic probation because of this latest violation and she pays Spencer a very angry visit.
Spencer insists that she only added pot, but Harper doesn't believe her. She informs the girl that she'll keep her from Princeton. In retaliation, Spencer reveals that she has a recording of Harper destroying the furniture of Ivy House during the potluck. Though she's been outsmarted, Harper promises that Spencer has no chance of getting into Ivy Eating Club. The two part on very bad terms.