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.
At first, Sakura would be in shock. Sasuke is someone she cares about deeply. But then she would start to analyze the situation. If she realizes Sasuke has some hidden motive, she might try to talk to him calmly, asking him why he's doing this. She could also use her intelligence to look for a way to escape while waiting for help from the Hidden Leaf Village.
Sakura's reaction could be complex. On one hand, she's a strong - willed ninja. So she would not just accept being kidnapped. She might try to break free immediately. But on the other hand, because it's Sasuke, she would also be curious about his reasons. She might try to appeal to the old Sasuke she knew, the one before he became so brooding and secretive, in an attempt to make him see the error of his ways and let her go.
He could also be initially confused. Sasuke has known Sakura for a long time, and this unexpected act from her would leave him wondering about her motives. He may hold back his anger for a while to hear her out and understand why she did such a thing.
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.
One possible plot could be that Sasuke has some sort of misunderstanding. Maybe he believes Sakura has some information about a threat to Konoha that she's not sharing, so he kidnaps her to force her to talk. Then Sakura tries to convince him that he's wrong while also trying to understand why Sasuke has become so extreme.
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.
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 She could become withdrawn herself, losing some of her usual cheerfulness.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 would likely be initially terrified but quickly regain her composure. She is a trained ninja after all. She might start by assessing her situation, looking for any weaknesses in Team Hebi's defenses or any possible escape routes. Sakura would also try to talk her way out of the situation, using her intelligence to reason with Team Hebi. If that doesn't work, she would be ready to fight back using her taijutsu skills and any medical ninjutsu that could be used offensively, like her chakra - enhanced strength punches.
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.
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.
Sakura might be heartbroken at first. She has always been in love with Sasuke and to find out he's cheating would shatter her world. She could become withdrawn and focus more on her medical ninjutsu as a way to cope.
The other members of their team or the village might have mixed reactions. Some might side with Sakura, understanding her point of view, while others might think she's being hasty or that they should try to preserve the relationship for the sake of the village's stability or their own friendship circle.