There's a Bat in Bunk Five

Blurb

There’s a Bat in Bunk Five is a young adult novel written by Paula Danziger.
In this sequel to The Cat Ate My Gymsuit, Marcy Lewis finds herself as a counselor in training at the summer camp near Woodstock, New York run by her former English teacher, Ms. Finney, whom Marcy has missed after Ms. Finney had been fired from her job. Marcy not only has to deal with the sudden attentions Ted, her new boyfriend, but when she has to go to Woodstock he starts hanging out with Betty, who has a crush on Ted. Marcy has lost a lot of weight and is now being noticed by boys. At the camp she is put in charge of a group of young girls whom she is expected to shepherd through the beginnings of adolescence. When she finds a bat in her bunk, and she is sure that this summer will be a summer to remember for eternity.
She also loves to read and write, and she tried to be Ginger's friend, who only likes Barbara Finney. After various trials and tribulations at the camp she gets fed up with people letting her down and being mean to her. Then all the girls in Marcy's bunk trick her into thinking there is another bat.