At first, Sakura may be terrified. Snakes are not exactly friendly creatures, and being tied up by them would be a scary experience. But as she calms down, she might start to analyze the situation. She could realize that Sasuke's actions might be a result of some external influence or a misunderstanding. So, instead of panicking, she may try to communicate with Sasuke through her words. She could tell him about their past together, their time as teammates, and how they have always been there for each other in some way. This might be her attempt to reach the real Sasuke behind the cold exterior and get him to release her.
Sakura could also be more composed in her reaction. Given her growth as a character, she might try to reason with Sasuke first. She could say things like 'Sasuke, I know you must have a reason for this. Let's talk about it.' However, if Sasuke doesn't respond or seems hostile, she may start to feel betrayed. She might then use her medical ninjutsu knowledge to try to find a weakness in the snakes or in Sasuke's technique that is keeping her tied up. She could also start thinking about how she can turn the situation around and make Sasuke see reason.
It would severely strain their relationship. Sasuke's act of tying Sakura with snakes is a very aggressive and demeaning act. Sakura would likely feel betrayed and terrified. This could lead to her having a deep - seated hatred for Sasuke, or at least a great deal of wariness and distance. Their relationship, which was already complex, would become even more so, with Sakura possibly vowing to never trust Sasuke again.
In this fanfiction, it could be that Sasuke has lost his mind due to some traumatic event. He ties Sakura with snakes because he sees her as a symbol of the world he wants to reject. The snakes could represent the chaos and danger that he now associates with her. Meanwhile, Sakura might be in shock at first, but then she starts to analyze the situation. She realizes that Sasuke is not in his right mind and tries to use her medical knowledge and ninja skills to not only free herself but also to heal Sasuke's broken psyche.
One possible reason could be a misunderstanding. Maybe Sasuke has been misled to think Sakura is a threat to him or his goals at that moment. In the Naruto universe, Sasuke has often been on a solitary path filled with suspicion. He might tie her up to keep her from interfering with something he's about to do. Another aspect could be related to some kind of test. He may want to see how Sakura will react in such a difficult situation to gauge her growth as a ninja. It could also be a part of a plan to protect her from something more dangerous, by restraining her movement in a way that he believes is the best for her safety, using the snakes as a means to immobilize her as he is known for his snake - like jutsu.
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.
She could also be shocked and a bit scared at first. But then, her medical ninja training kicks in. She might analyze the situation quickly, looking for weaknesses in the snakes' grip. Maybe she tries to use her knowledge of the human body (since she's a medic) to find a way to make the snakes loosen their hold, like targeting pressure points on the snakes if they have any.
Sakura could also try to stand up for herself. If she believes that Sasuke is being unfair in his anger, she may argue back. For instance, if Sasuke is angry because of a misunderstanding, Sakura might try to clarify the situation and prove her point.
She may initially be angry. Sakura is a proud and strong character. She could confront Sasuke and Ino, demanding an explanation. After that, she might decide to become even stronger, both in her ninja skills and her emotional resilience, to show Sasuke what he's missing.
In some fanfictions, Sakura's reaction could be more complex. She might be hurt not just physically but also emotionally. This could lead her to question her relationship with Sasuke and might cause her to make some big decisions, like whether to continue trying to reach out to him or to cut him off completely.
Sakura might be heartbroken. She's been in love with Sasuke for so long. She could initially go into denial, thinking it's just a temporary thing. Then she might get angry and vow to prove herself to Sasuke, perhaps by becoming an even stronger ninja.
She could be heartbroken. Sakura has always loved Sasuke deeply, so his leaving for Naruto would be a huge blow to her. She might initially be in denial, not believing that Sasuke would choose Naruto over her.