Sasuke could have immediately gone to comfort her. Despite his often cold exterior, he might have softened in that moment. He could have put his arm around her or just said some soothing words to calm her down.
Perhaps she was scared or in danger. In the fanfic world, there could be an enemy around and she was trying to hold in her fear until Sasuke heard her. It's possible that she was facing a powerful foe and was afraid for her life or the lives of her friends.
In some fanfics, Sasuke might initially be shocked. He could then feel a mix of joy and fear. Joy because he's starting a family with Sakura, but fear because of the responsibilities and potential dangers that might come with it.
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.
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 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.
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.
Sakura would probably be initially very angry. She has strong feelings for Sasuke, but kidnapping is a very extreme act. So she would likely fight back, using her medical ninjutsu skills and combat abilities to try and escape.
Sakura could initially be shocked and then try to change herself. She might think that if she becomes more like what Sasuke wants, he won't find her annoying anymore. So she could start to be more reserved and less pushy in her interactions with him.
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 She could become withdrawn herself, losing some of her usual cheerfulness.
On the other hand, Sasuke could be very stoic about it on the surface but internally be in turmoil. He might start to analyze his own actions and whether he had missed any signs from Sakura. He could also be the type to immediately start thinking of ways to win Sakura back if he realizes he can't stand the thought of her with someone else.