The Baby-Sitters Club #4: Claudia and Mean Janine by Ann Martin
Claudia and her sister, Janine, may as well be from two different planets. Claudia, who pays more attention to her artwork and The Baby-sitters Club than her homework, feels like she can't compete with her perfect sister. Janine studies nonstop, gets straight As, and even takes college-level courses! But when something unexpected happens to the most beloved person in their family, will the sisters be able to put aside their differences?