Another possible reason is that Sasuke is a bit insecure. She might not feel good enough for Sakura compared to other characters. So when she sees Sakura showing interest in others, she gets jealous because she thinks she's not measuring up. This insecurity can drive her jealousy and also lead to character development in the fanfiction as she tries to overcome it.
One reason could be that Sasuke really values Sakura's friendship and is afraid of losing it to someone else. Maybe she sees others getting closer to Sakura and feels left out.
One possible reason could be Sasuke's continuous absence due to his solo missions. He's always away, leaving Sakura feeling lonely and neglected in their relationship. This lack of emotional and physical presence can gradually erode the bond between them.
In fanfiction, Sasuke might snap at Sakura due to miscommunication. Sakura could be expressing her concern for him in a way that he misinterprets. For instance, if she tells him not to go on a dangerous mission and he thinks she is trying to control him instead of just caring about his safety. Another factor could be the influence of external forces. Maybe there are other characters or events that put him in a bad mood, and Sakura just happens to be there at the wrong time, so he snaps at her.
One reason could be that Sasuke is very popular and has a lot of fangirls. In the fanfic, Sakura's boyfriend might feel insecure because Sasuke has this charm that attracts everyone. Maybe Sasuke is always achieving great things and getting a lot of attention, which makes the boyfriend jealous as he might feel he can't compete with Sasuke in terms of popularity and achievements.
It could also be related to Sakura's strength. Sasuke is constantly striving to become stronger. If Sakura somehow shows a weakness or makes a mistake during a fight that he thinks could have been avoided, and it has negative consequences for their situation, he might get angry at her for not being more capable.
Perhaps Sakura is jealous because of her own insecurities. She might be comparing herself to both Naruto and Ino. Naruto has his own charm and strength, and Ino has her grace and popularity. Sakura, who might be struggling with her own self - worth, could see their interactions and feel envious, thinking that they are better off without her or that they have something she doesn't.
In the fanfiction, Sakura could be jealous because she has an ego. She might have thought that Naruto would always be there waiting for her. But when he falls for Hinata, it bruises her ego. Additionally, she may have seen Naruto as her safety net, someone who would always support her no matter what. Losing that special status to Hinata makes her envious and jealous.
Protectiveness. Sasuke has seen a lot of danger in his life. He knows Sakura is a valuable person, both as a friend and as someone he cares about. So his possessiveness could stem from his desire to keep her out of harm's way. He doesn't want any bad guys to get near her.
Well, one reason could be Sasuke's continued obsession with his revenge. He might be so focused on it that he ignores Sakura's feelings and concerns, which could lead to a fight. For example, if Sakura tries to persuade him to let go of his revenge and he refuses, it could spark an argument.
Perhaps Sasuke starts to notice Ino's unique skills and how they complement his own. Ino has her mind - related jutsus which could be useful in certain missions or battles. This practical aspect, combined with a growing personal bond, might lead him to leave Sakura for Ino.
One possible reason could be his sense of duty. Sasuke has always been driven by his goals for the village or his personal vendettas. Maybe he feels that his mission is more important than staying with Sakura and their unborn child, believing that his actions are for a greater good that will ultimately protect them as well.