This is a secondary character who appears in one animatic. The script is four pages long, and this character has about 1/3 of the dialogue.

Rebecca is an 11-year-old girl who falsely believes that she is seen as a queen bee figure, and nobody has the heart to correct her. She paradoxically thinks that she's both perfect and an utter failure, which causes her to come across as confusing and unpredictable, especially given her incredibly short temper. She is also the manipulative type, and will sometimes convince her friends that she is allowed to use them as punching bags.