- "The second I looked at her... everything changed. My whole universe changed."
- —John Diggle on Sara[src]
As a result of Barry Allen's alteration of history, creating and then trying to revert the Flashpoint timeline, Sara was erased from existence; in the post-Flashpoint timeline, John and Lyla instead have a son, John Diggle, Jr..
Sara is doted on by both her parents, especially her father, who once claimed he could watch her forever. He is also very protective of his daughter; when Lyla asked what John plans to do when Sara discovers boys, he jokingly responded, "that's what [his] Glock is for."
Sara was introduced to Team Arrow's secrets early on when John brought her to the Arrowcave while Lyla was on an A.R.G.U.S. assignment in Santa Prisca and her nanny called in sick. Oliver Queen protested that he wasn't comfortable with Sara being in the Arrowcave, though John argued that she wouldn't be able to tell anyone. At Felicity Smoak's suggestion, Sara was cared for by the former's mother, Donna. Donna and Sara stayed at Felicity's apartment until an A.R.G.U.S. agent picked up Sara.
Sara was present at her parents' wedding in March 2015 and was a major influence on their career decisions; when her parents returned from Kasnia following Deadshot's sacrifice, Lyla resigned from A.R.G.U.S., having grown disillusioned with the corrupt agency, while John resolved to stay with Team Arrow, both determined to set a good example for their daughter.
Several weeks later, Sara and her parents had dinner Felicity and Thea Queen. She seemed to like Felicity and Thea, who fed and played with her. Soon after, Lyla was abducted by the League of Assassins, leaving Sara alone in the apartment. She was crying in her crib when Felicity and John found her. They left Sara in the care of her parents' neighbor while working to rescue her mother.
In early 2016, Sara met her uncle, Andy Diggle, for the first time after he redeemed himself by saving John and Lyla's lives and helped bring down his former CO, Lieutenant Joyner, and Shadowspire.
Erased from existence and aftermath
When Barry Allen went back in time to prevent his mother's death, he created an alternate timeline known as "Flashpoint". Sara's status in the Flashpoint timeline is unknown, but when Eobard Thawne helped Barry restore the previous timeline, some less obvious changes remained. One of the major ones was the erasing of Sara from existence; in this new timeline, the Diggle family instead has a son, John Diggle, Jr.
During the Dominators' invasion, Barry revealed the existence of Sara in the previous timeline to John, Lyla, Team Arrow, Team Flash and the Legends. As a result, John and Lyla became somewhat estranged from Barry (even though they have no memories of ever having a daughter) but eventually forgave him once he regained their trust.