Who is sheila borden in Things not Seen?

In "Things Not Seen" by Andrew Clements, Sheila Borden is a pivotal character who becomes a close friend to the protagonist, Bobby Phillips. She is a clever and resourceful teenager who helps Bobby navigate the challenges he faces after becoming invisible. Sheila's support and understanding play a crucial role in Bobby's journey, as their friendship develops and deepens throughout the story. Her character embodies themes of trust, loyalty, and resilience.