Hilary is Tyson and Kenny's classmate. She is also the class President. She loves to bully Tyson. Tyson calls her the "Wicked Witch Of The 8th Grade", which usually earns Tyson a beating or punishment from her.
At first she thought Tyson useless, but when she and Kenny got kidnapped, she realised that Tyson wasn't as bad as she expected. After that she started hanging around them.
At first she couldn't see bitbeasts and it frustrated her to no end. And the guys too.
She and Tyson fight a lot, but they're also great friends. She's the coach of the team. In G-rev, she becomes their assistant coach as Hiro takes the main position.