Sakura may initially be paralyzed by fear, but then her love for Sasuke and her own determination to survive could kick in. She might try to counter - attack in a non - lethal way, hoping to subdue Sasuke rather than harm him. She could also call out to their shared memories in an attempt to stop him from actually killing her.
Sakura might be in shock. She probably couldn't believe that Sasuke, someone she cares about deeply, would try to kill her. So she could be frozen in place for a moment, unable to react immediately.
He might be initially confused. Sasuke is not used to Sakura ignoring him as she has always been somewhat persistent in her attention towards him. So, he may be at a loss as to why she is suddenly acting this way.
She might be initially heartbroken. Sakura, being in love with Sasuke, would surely be deeply affected when he neglects her. She could become withdrawn herself, losing some of her usual cheerfulness.
Sakura could be a bit angry at first. She has grown and become more independent during his absence. When Sasuke shows regret, she may lash out, expressing all the pain and frustration she felt during his long absence, but deep down she still has feelings for him.
At first, Sakura might be terrified. After all, being kidnapped is a scary situation. But then, depending on her character development in the fanfiction, she could start to try and reason with Sasuke. She might ask him why he's doing this and try to get him to see the error of his ways.
Another reaction could be that Sakura becomes more determined. His yelling could fuel her desire to prove herself to Sasuke, whether it's in terms of her strength, her loyalty, or her understanding of him. So instead of being deterred, she uses it as motivation to grow and change in the eyes of Sasuke.
Perhaps Sasuke was testing Sakura's loyalty or strength. He may have thought that if she couldn't withstand his aggression, she wasn't worthy of being in his life. Also, his own inner demons, like the hatred he carried from his past, could have flared up and led him to almost kill her without fully realizing what he was doing.
Naruto might initially be shocked and confused. He has always considered Sasuke as a friend, so Sasuke's sudden attempt on his life would be a huge blow. He may try to talk to Sasuke first, to understand why he is doing this.
In some fanfictions, Sakura may be determined to find Sasuke and bring him back. She could set out on her own journey, facing various challenges along the way, and growing both as a person and as a ninja in the process of trying to reunite with him.
Another reaction could be that Sakura tries to follow Sasuke. She believes that she can change his mind or that she can be of help to him. She might leave her own responsibilities behind for a while to chase after him, thinking that their bond is strong enough to overcome whatever is making Sasuke leave.