At 23, she is not much older than the teens in the support groups she leads in Pawtucket and Fall River, Massachusetts. They meet to talk about grief, a subject Sarah Cordeiro of Tiverton would give anything to not be an expert in. In 2008, when Cordeiro was 13 years old, her 11-year-old sister, Megan, died 18 months after being diagnosed with acute myelogenous leukemia and eight months after a bone marrow transplant.