Leanne was a witch and a student in Hufflepuff House at Hogwarts School of Witchcraft and Wizardry, a contemporary of Harry Potter. She was a close friend of Gryffindor student Katie Bell and a member of Dumbledore's Army. Leanne is most notable for being the primary witness to the attack on Katie Bell by a cursed Opal Necklace during their sixth year and for her participation in the Battle of Hogwarts.
Leanne's early life and family background are unknown. She attended Hogwarts during the same period as Harry Potter.
Leanne's house affiliation was confirmed when Ron Weasley identified her to Harry as a Hufflepuff. She joined Dumbledore's Army in her fifth or sixth year, where she was taught defensive magic by Harry. In her seventh year, during a trip to Hogsmeade, Leanne and Katie were returning to the castle from the Three Broomsticks when Katie, who was carrying a mysterious package, began to argue with Leanne. The package contained a cursed Opal Necklace intended for Albus Dumbledore, which Katie had been placed under the Imperius Curse to deliver by Draco Malfoy. Leanne, sensing the danger, tried to stop Katie from taking the package back to the school. During their struggle, the package tore, and Katie's hand brushed against the necklace through a small hole in her glove. Leanne witnessed the horrific effects of the curse as Katie was lifted into the air, screaming, and thrown about as if by an invisible force before collapsing. Leanne was hysterical but was able to provide an account of the event to Harry, Ron, and Hermione Granger, explaining that Katie had gotten the package from someone in the toilets of the Three Broomsticks.
Despite the dangers of the Second Wizarding War, Leanne answered the call to defend Hogwarts on 2 May 1998. Her membership in Dumbledore's Army and her loyalty to her friends brought her back to the castle. During the Battle of Hogwarts, she was seen fighting alongside other students, duelling a masked Death Eater near the entrance to the Great Hall. Her ultimate fate after the battle is not mentioned in the novels.
The books provide no description of Leanne's physical appearance. Leanne was a loyal and caring friend, deeply concerned for Katie Bell's safety when she tried to prevent her from handling the dangerous package. While she could be frightened by terrifying events, as shown by her hysteria after Katie was cursed, she was also exceptionally brave. Her decision to return and fight in the Battle of Hogwarts demonstrates her courage and her commitment to Dumbledore's Army and its cause.
As a member of Dumbledore's Army, Leanne received training in practical defensive magic that went beyond the standard Ministry-approved curriculum of the time. Her ability to hold her own against a Death Eater during the Battle of Hogwarts suggests she was a competent duellist who had mastered the spells taught by Harry Potter. No specific spells, wand details, or Patronus Charm form are known.
The name Leanne is a modern English name, often considered a combination of Lee (from an Old English surname meaning “clearing” or “meadow”) and Anne (from the Hebrew name Hannah, meaning “grace” or “favour”). The name does not have a specific, overt connection to her character traits beyond perhaps suggesting a generally pleasant nature.
In the film adaptation of Harry Potter and the Half-Blood Prince, Leanne is portrayed by actress Isabella Laughland. The scene where Katie Bell is cursed is depicted similarly to the book, with Leanne trying to stop Katie and witnessing the horrifying effects of the Opal Necklace (film).