Naruto, being the friendly and optimistic one, would likely be excited for Gaara. He might encourage Gaara to be more open about his feelings towards Sakura. He could offer advice based on his own experiences with Hinata. Sasuke, though, would probably be aloof. He has always been more focused on his own goals and revenge. He might view Gaara's crush as a distraction for Gaara and tell him to focus on more important things, like protecting his village. However, deep down, he might also hope that Gaara can find some happiness.
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.
He may also choose to defend himself without really fighting back. Naruto values Sakura as a friend and teammate, so he would be reluctant to harm her. He might just try to dodge her attacks and keep talking to her, hoping to snap her out of it.
Naruto might initially be in denial. He's so used to having Sakura around and believing that they have a future together. So when she leaves for Sasuke, he might think it's just a temporary thing or that she's been influenced by something or someone. But as time passes and he realizes it's real, he would be deeply hurt. He might also start to question his own self - worth, thinking that he wasn't good enough for Sakura. And he might even try to win her back at first, but then slowly come to accept the situation and focus on his other responsibilities like being a ninja and protecting the village.
Well, in many fanfictions, it might start with Gaara noticing Naruto's unique strength and unwavering spirit. Naruto's ability to reach out to others, even his enemies, could be very appealing to Gaara. Maybe during a joint mission, they have to rely on each other, and Gaara starts to see Naruto in a different light, gradually developing deeper feelings as they spend more time together.
Well, Naruto might be furious. He's always been protective of Sakura. He'd probably drop everything he's doing and go after Sasuke to rescue Sakura. Naruto has a strong sense of justice and loyalty, especially towards his friends. And Sakura is one of his closest friends, so he won't stand by and let her be in danger.
In many Sasuke - Sakura - Gaara fanfictions, Sasuke saving Sakura from Gaara can be a really exciting plot. It often shows Sasuke's strength and his hidden feelings for Sakura. Maybe he uses his Sharingan to outwit Gaara's sand attacks and rescue Sakura just in time.
A fanfiction could be set in a post - war scenario. Sasuke is trying to atone for his past actions and Sakura is by his side to support him. Meanwhile, Gaara, as the Kazekage, invites them to the Sand Village. Hinata also comes along. Here, they all train together. Hinata's gentle nature starts to soften Gaara's tough exterior and Sasuke and Sakura grow closer as they see the potential for a new, peaceful future. This could lead to new relationships forming between the four characters.
Sakura would be over the moon. She would blush deeply and look at Sasuke with so much love in her eyes. She might be at a loss for words for a moment, but then she would find her voice and tell Sasuke that she has been waiting for this moment her whole life. She would also feel a sense of pride that Sasuke has chosen her, after all they have been through. And she would immediately start thinking about how to share the good news with their friends, especially Naruto, who has been like a brother to her and has also been a part of their journey.
Sakura might be initially frustrated. She's used to Sasuke being in control, so seeing him drunk could be a bit of a shock. But then she'd probably feel a sense of protectiveness and try to sober him up.
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.