Sarada might be initially shocked and sad. She loves both her parents, and the divorce would be a huge blow to her. She could become withdrawn for a while, not wanting to talk to her friends about it.
Itachi would probably be very calm and composed. He might see Sarada as a symbol of the new generation of ninjas in the village. He could be gentle with her, perhaps sensing her potential and her desire to grow as a ninja.
The Bnha universe's reaction would be mixed. Those who are into complex stories, like Todoroki, might study the relationships in Hamilton fanfiction. But others, like Mineta, might not be interested at all because it doesn't have much to do with his usual interests. Overall, it would depend on the individual characters' personalities and interests.
Some would be inspired. Characters like All Might might see Peter Parker's journey as similar to his own in some ways. Both are trying to do good in a world full of challenges. All Might could appreciate Peter's determination to protect his city despite having a normal life outside of being a hero.
For heroic - centric fanfictions, they would likely be disdainful. Since they oppose heroes, seeing stories that glorify heroes would annoy them. They might scoff at the idealized versions of heroes in those fanfictions.
Naruto would probably be extremely happy and excited. He has always been close to Sakura, and seeing her become a mother would be a big moment for him. He might be there to support her during the birth, bringing some of his positive energy to the situation.
The ninja world would likely be filled with a mix of reactions. Some would see it as a positive sign of unity between different clans. Others might be worried about the power the baby could potentially have. There could be those who would try to use the baby for their own political or power - hungry motives.
Sasuke would likely be initially shocked. He's a man who has been through a lot and is used to a life of solitude and danger. But then, a sense of protectiveness would kick in. He'd become more vigilant about the safety of Sakura and their unborn child. He might also start to think about how to be a better father than his own was, in some ways, trying to break the cycle of his family's past.
They might be overjoyed. Since Sarada is part of their family, they would likely welcome her with open arms and big smiles. They could be very proud of how far she has come in her ninja training.