In some ways I think that Jessi and the Bad Bay-Sitter is one of the few books that portraits the BSC and their classmates realistically. When Dawn moves back the California the first time, the BSC desperately needs help (and they don't even know that Mal is about to develop mono and also be out for awhile). Jessi suggests that one of her classmates joins the BSC to help out. Wendy seems interested in the club, but doesn't even come close to meeting their high expectations- she comes to meetings late, she takes jobs without consulting the other members and is clearly not dedicated to the club. It's no surprise that she doesn't make the cut and only appears in this book.
Even though the situation stinks, I really like how the characters are portrayed in this book. Wendy is only eleven so it's easy to imagine her not being able to make a full commitment to a new club. It's also understandable why she wouldn't do well sharing her clients with 6 other baby-sitters. On the other hand it's easy to see Kristy's point of view. She has the process of baby-sitting so streamlined that when someone breaks the rules she often over reacts.
I first read these books when I was about seven. In my head I thought that 13 was going to be this wonderful age where I would suddenly be all kinds of mature and given tons of responsibility, just the The Baby-Sitters Club members. Of course I would realize that this wasn't the case. Though the characters in this book are still portrayed more mature than the typical eleven and thirteen year olds, I think their actions are closer to how girls those ages would act and react. This was one of the books that I re-read a lot as a kid and was probably my favorite book starring Jessi, after Jessi Ramsey Pet-Sitter. Of course you know that I am going to recommend this book, so I guess I will stop babbling about how great the series is.