One possible scenario in a fanfic where Sally dies is that Percy loses his connection to his 'normal' life. Sally was always his anchor to the mortal world. Without her, he might feel adrift. He could start to question his own identity more. Is he just a demigod or was Sally a big part of what made him who he is? This could lead to some interesting character development, like him trying to find a new purpose outside of just being a son of Poseidon and a hero.
In some fanfictions where Sally dies, it could lead to Percy being filled with a new kind of rage and determination. He might become more withdrawn at first, shutting out his friends as he grapples with the loss. But eventually, it could fuel his growth as a hero, making him more fearless in the face of danger because he has already lost the most important person to him.
Well, if Sally dies in a fanfic, it would be a huge turning point for Percy. Maybe he blames the gods more than ever. He could go on a quest not just for the usual reasons but to get some sort of revenge or justice. His relationships with other characters like Annabeth would also be strained as he's dealing with this massive grief. It would change the whole dynamic of the story.
Chapter 191, "Repelling the Enemy and Punishment, The 1st Wedding", is the clearest early answer because it turns Leader Xia Hong's situation into a concrete plot event. It opens with Seven-maned Power, this Chen Yingyuan, is actually not even as good... and closes on His opponent's intention was clear, to not allow him to speak..
Chapter 263, "Strategizing, An Elder Brother Is Like a Father", is the clearest early answer because it turns Xiao Ning's situation into a concrete plot event. The chapter gives readers a real answer by opening on Upon hearing Xia Hong's inquiry, Xiao Ning's face turned red at once. and ending on Currently in Great Xia, only Xia Hong as the leader is qualified to....
Chapter 304, "The Defeated Longyou Army, Xia Army Cannot Escape, Holy Tripod", is the clearest early answer because Long Mountain gets a payoff that changes the stakes. It opens with The people's expressions, which were originally somewhat dispirited,... and closes on Long Mountain originally had just over 70,000 people.. The key payoff is that the chapter closes with "Decisively defeat the Xia Army!, which gives power growth a stronger narrative position and pushes the power growth onward.
Chapter 250, "Rescue, Intimidation, and Surprise (Part 3)", is the clearest early answer because it turns Great Xia's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The young master brought so many Cold Resistance Level soldiers,... and follows through with After a glance at each other, their eyes showed a noticeable firming....
Chapter 261, "The Shock of Peng Bo and Chen Yingyuan, Great Xia Martial Gathering (Part 3)", is the clearest early answer because it turns Aunt Mei's situation into a concrete plot event. The chapter turns that into something concrete by moving from Liu Ming might simply think that his grandfather is not too... to The price of beast meat has been lowered, now 1 contribution point....
Chapter 203, "Shock, Prisoner Rules, and What Constitutes Guilt?", is the clearest early answer because it turns Flying Tiger Camp's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Four families, numbering five to six thousand people, gradually... and follows through with Father, don't worry, I'll go plead with them!" Xiang Liang said....
Chapter 195, "Jade Bone, Conclusion, Cultivation Dilemma", is the clearest early answer because it turns Twelve Manes's situation into a concrete plot event. The setup is After Snow Mane's bone was severed, a thick smoke billowed out, but..., but the pressure keeps building through Once the bone was cut, Snow Mane's right forelimb was connected to....
Chapter 197, "Cloud Jiao Advances, Beast Blood Dosage", is the clearest early answer because Qiu Peng finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with Qiu Peng fell silent upon hearing the voice, remembering clearly that... and follows through with Xia Hong turned his head and looked at Xia Chuan inside the silent....
Chapter 215, "Teaching Luo Cheng Techniques, News of the Jade Bone (Part 2)", is the clearest early answer because Luo Cheng gets a payoff that changes the stakes. A useful checkpoint is the way the scene starts with He lived not far from Luo Ming's residence. and follows through with In the courtyard, were astonishingly three Cold Beasts, specifically....
Chapter 202, "Worthless Foes, Four Clans Bow Down (Part 2)", is the clearest early answer because it turns Lu Yang's situation into a concrete plot event. Early on, From the initial shock, Xiang Liang had become numb.. By the end, Tomorrow is the New Year, and time is tight..