Heidi Darling is the daughter of Mr. Darling, the owner of Java Heaven. Heidi is an over achiever whose parents push her to be perfect in everything she does. For this reason, Heidi is often held up as an example to Katrina by the guidance counselor and other teachers. This creates resentment in Katrina and her fellow classmates. However, it is clear by the end of the novel that Heidi is just as unhappy in her own over achievement. Heidi turns out to be a fairly nice girl whom Katrina finds a way to accept for Vincent's sake.
