Joe She's ok. There's a sequel called "There's a Bat in Bunk Five" where Marcy loses weight, becomes a summer camp counselor, and falls in love for the first time. I recall it was as good as "...Gymsuit".
Rosa Yes. She's gained character and friends, and her mother is a stronger person too. She's stopped turning to ice cream to ease her pain. Her dad isn't quite as big of a bully as he was, now that both Marcy and her mother have stood up to him. And she still has her little brother to look after, and he looks after her, too. She'll be alright.