Leah is a frenemy of Hannah.
Leah seemed to be Hannah's friend until Hannah didn't give her phone to Leah to record Rachel getting her shirt stuck in her locker. Then she became Hannah's bully and threatened her in any way she could. Darbie and Kelly attempted to get revenge by putting her on a karma spell so anything she did to Hannah would happen to her instead. Hannah and Leah ultimately resolve by the end.