Phoenix Rising: Or, How to Survive Your Life — Cynthia D. Grant

In ten years, Jessie will be twenty-seven -- but her sister Helen will always be eighteen...

Jessie's not ready to move on. Everyone says she's doing great, but she is drowning in grief and hiding it with her characteristic wisecracks. Why tell anyone? It's not like it will bring Helen back. Jessie can see that her whole family is barely treading water: Her brother Lucas has completely shut down, and her parents are just going through the motions of life.

Then Jessie finds Helen's diary, the one she was keeping up until her death. Desperate to feel close to her sister again, Jessie reads through the entries, discovering truths about Helen -- and herself -- that she never expected.