Isabelle Lee (Belle Lee, Belly) is a sad kid, just like Finn from book #125. Finn's grief became depression which manifested in withdrawal, Isabelle's grief manifests as body hate and bulimia.
Winner of the Milkweed prize for Children's Literature, this body-positive book is a great recommendation for someone in your life who might be turning their frustrations towards their bodies.
Perfect by Natasha Friend.
PS: Since I read these two books back to back I can't help but compare them and I wonder why college students are assigning me books that are intended for an audience 1/4 my age.