The following version of the book was used to create this study guide: Murphy, Julie, Dear Sweet Pea, HarperCollins Publishers, New York, New York, 2019. Kindle AZW file.

Patricia “Sweet Pea” DiMarco is a 13-year-old seventh grader who is dealing with some serious changes in her life. The most striking is that her parents divorced after her father, Andre, came out as gay. Her parents now live in almost identical houses on the same block. In a small town where everyone knows everyone, the divorce is big news, especially because Sweet Pea's mother, Liz, is a therapist. Sweet Pea is struggling with the situation and that struggle becomes desperate when she learns that her father has taking up art as a hobby and is planning a move while her mother is starting to date. Sweet Pea is able to cope with these changes in the beginning because of the steadfast friendship of Oscar Rivera. Oscar lives nearby with his parents and his two older brothers. Oscar is always in Sweet Pea's corner, unlike her former best friend, Kiera Bryant. Kiera and Sweet Pea were best friends until they inexplicably grew apart the previous year.

Sweet Pea's neighbor is Miss Flora Mae, an advice columnist who lives between Liz and Andre's “mirror houses.” When Miss Flora Mae is called away on family business, she hires Sweet Pea to take care of her mail and her plants. Sweet Pea initially sees this as a dreaded chore, but she quickly begins to enjoy being at Miss Flora Mae's house, listening to music she has never heard and scrolling through the letters from people asking for advice. When Sweet Pea recognizes Kiera's handwriting, she learns that Kiera's parents are constantly fighting and that Kiera fears they are going to divorce. Sweet Pea is inspired to answer Kiera's letter, and she is pleased when she feels she has given good advice. She continues to answer an occasional letter, believing that Miss Flora Mae will never know. To one disgruntled writer, she advises that he ignore the person who no longer seems to be his friend. She is then surprised to learn that Oscar wrote the letter and he is taking her advice.

When Miss Flora Mae returns, she makes it clear that she knows that Sweet Pea answered some letters, and she compliments Sweet Pea for giving good advice. She then directs Sweet Pea toward accepting the changes in her life and mending her relationship with Oscar. As the novel comes to a close, Sweet Pea camps out on Oscar's porch until he forgives her for being careless with their friendship. She also accepts that her parents as individuals who have a right to a life of their own. They will continue to be her parents, no matter what else takes place in their lives.