Despite Sakura's suspicions of Sasuke upon his arrival to the war battlefield and her open distrust and uncertainty of Sasuke's motives, Sakura (and Naruto) went along with it, pretending they were a whole team again despite the deep tensions and uncertainty between them as she tried to discern his true intentions.
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Sakura using herself as a diversion could be viewed as testing her hypothesis: is Sasuke here for me and Naruto, or for something else? Sakura already directly questioned Sasuke's motives earlier during the war, but he wouldn't tell her anything, so Sakura is left to her own guesses and theories.
Considering that Sasuke was her former teammate and one of her closest friends, Sakura wanted to believe getting him back would be easy now that they were allies. If you've ever hoped for something, even something farfetched that you knew was impossible, than you know how devastating losing that hope can be, even if it was only a slim hope to begin with. Even when you know you shouldn't get your hopes up, your heart gets ahead of your head and it's a devastating blow when those hopes are dashed.
I think that's what's going on with Sakura here. She knows she should be suspicious and distrustful of Sasuke (and she was), but that's not what she wants. Against her better judgement, Sakura's hopes begin to rise that maybe Sasuke is there for her and Naruto because there is no other clear explanation for why he appeared there on the battlefield.
But when she impales herself on Madara, Sasuke doesn't flinch or try to save her. With that, Sakura's hopes that Sasuke may be there for her and Naruto are completely dashed, and she's left with concerning question: Sasuke isn't there for Team 7, so why is he there, and what is his endgame motive?
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Sasuke didn't fret or show concern over Sakura's welfare, but Sasuke isn't one to fret over allies. Several of his allies have been injured in the war, but Sasuke hadn't faltered for an instant, even when his allies are dropping like flies around him the Allied Shinobi Forces' morale was at an all-time low, he gives the appearance of being emotionally unmoved.
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Considering his experience watching every single one of his beloved clanmate comrades die, and later being exposed to the horrors of Orochimaru's inhumane experimentations, Sasuke has become a lot more callous than his peers, because over the years he's been exposed to the suffering of people and had to grapple with not being able to save everyone.
Additionally, Sasuke treats his allies with the mutual expectations of a warrior: everyone out there should be willing to give their all or die for the cause. If an ally loses a limb to create an opening, Sasuke will take it. If an ally uses up all their chakra to create an opening, Sasuke will take it. If an ally is willing to die to keep the fight going, Sasuke will take it. At this point, Sasuke's idea of teamwork is not wasting the chances he's given by the sacrifices of others. If Sakura recklessly rushes into battle without consulting the others and gets impaled to create an opening, Sasuke is going to take it. And he does. Even though Sakura's abrupt action startled him and caught him off guard, he quickly recovered and used the opening she provided to slash at Madara. And that's Sasuke's idea of teamwork. He's not interested in protecting his fellow shinobi (who he believes should be ready and willing to take as many dangerous risks and contribute as much to the cause as he is), he's interested in winning. His whole plan at the moment is to be hated, so making friends and establishing good relations runs against his goals. Sasuke is brutally practical and utilitarian during this war, and it makes him lacking in compassion towards even his allies. Thus why he doesn't fret over the injured Sakura; she's a fellow warrior and it was her choice to recklessly rush at a powerhouse like Madara without consulting and planning with her comrades, and she incurred the consequences of her actions. Sasuke doesn't have healing abilities (but he knows that Naruto and Sakura do), so he isn't going to be the one to tend to Sakura's injuries because his skillset is useless there. Sasuke knows that Sakura has regenerative abilities and that she's fine. He is going to focus on the battle and keep his eye on the enemy, not on fretting over his comrade's injuries, especially if they're not even serious.
