Summer Mysteries: Berta

This German student acts as the voice of reason among Summer's friends. Or at least she tries to. The most studious of the girls, she has a broad array of knowledge and is rarely seen without a book in hand. Problem is, she likes to understand a situation before she does anything, leading to many, many occasions where she thinks when she should be acting. She is not usually consulted when ordering pizza.

What is "Summer Mysteries"?