Kimberly ''Kim'' Hubbard is Rachel Hubbard's twin sister.
When the girls' mother died, their father was flummoxed as to how to raise two girls on his own. Fearing that they may be put up for adoption, the girls applied for every scholarship that they could. The scholarship to Waverly Academy was the only one they successfully got, but only Rachel was accepted. Rather than separate, they chose instead to come up with a plan that would allow them both to attend. They discovered that their dorm had a secret panel that lead to an old unused storage room which they converted into a makeshift bedroom/study area for themselves. Each girl would attend classes that played to their strengths, and they did so well they became valedictorians. Unfortunately, one day Kim was too sick to attend one of her classes. Rachel covered for her, but as luck would have it there was a surprise pop quiz that she totally bombed, knocking them both out of the running.
Somehow, the Black Cat discovered the twins' secret and blackmailed them into leaving her warning notes for the other students. The Black Cat contacts them solely through email and uses a different IP address each time, making it extremely difficult to discover whose behind it.
One night after Rachel sneaks Kim a tray of food as usual, the secret panel in their room suddenly slides open, revealing the new student, Becca Sawyer. Rachel instinctively attempts to hide Kim from view, but its too late. Pretending anymore is useless, so the twins tell Becca about their story and the Black Cat's blackmail. Since Becca promises not to expose them, they ask her for help in discovering who the Black Cat really is.
The next time Becca speaks to one of the twins, she tries to guess which one she's speaking to. The ex-valedictorian is confident that Becca can't do it because she and her sister are identical in every way, even down to the handwriting. However, there's a trick to telling the two apart: Kim always tucks the stray lock of hair back into her headband while Rachel doesn't bother.
When the Black Cat is finally exposed and expelled, she makes sure that the twins are expelled as well. However, the school decides that their deception was born out of a desire to get a good education and offers a scholarship to them both.
- Kim's favorite subject is science.
- When asked on the school's website what her plans after college are, Kim (or possibly Rachel) says that she would like to see the world, but realistically, would probably be applying to medical school.