
The Summer I Turned Pretty Season 2 revealed the exact date of Susannah Fisher's death, and the timing is vital to Belly's romance with Jeremiah. Susannah (Rachel Blanchard) is an important character in the Amazon Prime Video series since she has direct ties to the core cast. She is Conrad and Jeremiah's mother, Belly's mentor and second mother, and Laurel's longtime best friend.
The Summer I Turned Pretty Season 1's final episodes dropped a bombshell about Susannah, confirming that her cancer is back. While she seemed unfazed about her condition, it was clear that the reveal shocked those around her (specifically Belly, Jeremiah, and Conrad). It placed Jeremiah and Conrad's relationship as brothers into a downward spiral after Conrad chose to keep it from him. Meanwhile, Belly was heartbroken over Susannah's condition.
Season 1 ended on a hopeful note, with Susannah agreeing to a new clinical trial that would've helped her survive her cancer. However, Season 2 confirmed that Susannah died after she succumbed to her disease, changing the story of Belly, Jeremiah, and Conrad forever.
When Did Susannah Die in 'The Summer I Turned Pretty'?

Susannah Fisher's death in The Summer I Turned Pretty (in the books and the series) changed every core character's narrative trajectory as they deal with grief and loss due to how important she is to the overall story. While Jenny Han's trilogy of The Summer I Turned Pretty novels didn't really reveal the exact date of Susannah's death, Amazon Prime Video's adaptation secretly confirmed when she died.
At the 33:37 mark of The Summer I Turned Pretty Season 2, Episode 3, one of the visitors at Susannah's funeral can be seen holding a pamphlet about the service, revealing that she died on April 14, 2023, in the series' timeline.

Months before Susannah's death, Season 2 revealed that Conrad and Belly had already started dating and were doing well as a couple. They even spent Christmas together in Cousins. However, at the beginning of the new year, it was apparent that Susannah's condition was getting worse, which clearly affected Conrad (because he was the one closest to his mother).
Conrad and Belly started to drift apart because he couldn't focus on his relationship with her due to Susannah's dying state. The pair's relationship dwindled during prom week (which is at the start of April - mere weeks before Susannah's death), and they eventually broke up.
Susannah's funeral was the first time Conrad and Belly saw each other after they broke up, which was still fresh in their minds (making it even harder for both of them).
Although Conrad tried to tell Belly, "No, it's not you. It has nothing to do with you," because he wanted to make her understand that he couldn't wrap his mind around Susannah's impending death, he didn't hesitate or try to stop Belly when she declared that they were over (Conrad explained his state of mind here in The Summer I Turned Pretty Season 3).
This breakup ultimately impacted Belly's decision to choose Jeremiah because she leaned on him for comfort after the traumatic events of Susannah's death and Conrad's falling out.
Why Susannah's Death Served as the Turning Point for Jeremiah & Belly

The grief over Susannah's death turned Belly into an emotional wreck, but Jeremiah was there to support her throughout. The shared grief was crucial in developing Belly and Jeremiah's bond, turning their friendship into something more.
The Summer I Turned Pretty Season 2 showed more of Belly and Jeremiah's love story as they worked together with Conrad, Steven, and Taylor to save Susannah's beach house in Cousins from being sold to a realtor.
The pair grew closer, much to Conrad's disappointment, but he chose not to stop them from being together because he still blamed himself for losing Belly in the first place.
Aside from their shared grief, Belly and Conrad's breakup paved the way for Jeremiah to enter the romantic picture, essentially setting up the status quo of The Summer I Turned Pretty Season 3.
While Jeremiah and Belly did break up during the first episode of The Summer I Turned Pretty Season 3, they made up and got engaged, much to everyone's disappointment, because they are still young.
This time around, Belly and Jeremiah's sudden engagement greatly impacted Conrad because he was still clearly in love with Belly after all these years.
Whether Belly and Jeremiah will end up together in the series remains to be seen, but it's clear after seeing Conrad's perspective in The Summer I Turned Pretty, Season 3, Episode 5, that he still has a fighting chance if he plays the cards right.