Katie Bell is one year above Harry Potter, and so she has been seen in all of the books, however briefly she was mentioned in the seventh.
She is a Chaser on the Gryffindor Quidditch team, alongside Angelina Johnson and Alicia Spinnet, all of whom Oliver has referred to as "superb." According to the HP Lexicon, Katie played her first game of Quidditch alongside Harry.
In the fall of 1996, Katie was placed under the Imperius Curse by Madam Rosmerta to carry a parcel containing a cursed opal necklace to Hogwarts. As she argued with her friend Leanne, the parcel broke, and Katie levitated, contorted with pain, and then fell back to the ground. She was forced to remain in St. Mungo's for part of her seventh year.
According to BabyNames.com, Katie is a Celtic/Gaelic name meaning pure or virginal
In the films, Katie Bell is portrayed by Emily Dale.