She might be overjoyed. After all, Naruto is her son. She could immediately rush to find him and embrace him tightly, tears of happiness streaming down her face.
One common plot is Kushina finding Naruto in a different time or dimension. For example, she might end up in the future where Naruto has grown up and she gets to see the kind of person he has become. It's an emotional and interesting concept as she gets to witness all his achievements and the challenges he has overcome.
You can try websites like Fanfiction.net or Archive of Our Own (AO3). On Fanfiction.net, you can simply search for 'Kushina finds Naruto' in the search bar and it will show you a list of relevant fanfictions. AO3 also has a large collection, and their tagging system can help you narrow down your search to find exactly what you're looking for.
One consequence could be a shift in the power dynamics. If Kushina is alive and now reunited with Naruto, they could form a powerful duo. This might make their enemies more cautious or even lead to new alliances being formed against them. Also, Naruto's morale would be greatly boosted, and he might become even more determined in his goals, which could speed up the overall plot development.
Well, one possibility is that Naruto would be overjoyed. He has always longed for his mother's love. He might spend days just talking to her, sharing all his experiences, from his training with Jiraiya to his battles against the Akatsuki. Kushina would probably be extremely proud of him and would start teaching him some Uzumaki clan jutsus that were passed down in the family. And Naruto's relationship with the village would also change. He would no longer be the orphan that everyone pitied. Instead, he would be the son of a hero, which could bring a whole new dynamic to his standing in Konoha.
One great fanfic could be 'Naruto's Reunion with Kushina'. In this fanfic, Naruto discovers a hidden jutsu that allows him to travel back in time and he meets his mother Kushina. It's a heartwarming story as they bond and Kushina gets to see the amazing person Naruto has become.
The exploration of Kushina's past is also great. A good fanfic will show how Kushina was before Naruto was born, her relationship with Minato, and her life in the Uzumaki clan. This gives more depth to the story. In some fanfics, Naruto also gets to experience some of her memories, which is really interesting.
Naruto's personality could become more confident and stable. With a mother figure in his life, he would have someone to turn to for emotional support. He might not be as impulsive as he was before because Kushina could give him advice based on her own experiences. For example, when dealing with conflicts in the village or with other ninja, he would think twice instead of jumping into action right away.
Naruto's reaction could be complex. On one hand, he would be happy to find someone else from his clan. He has always been proud of his Uzumaki heritage despite not knowing much about it at first. But on the other hand, he might be a bit cautious. Karin has been associated with some not - so - good groups in the past. However, overall, his positive nature would probably lead him to approach Karin with an open mind and try to build a connection with her based on their shared Uzumaki roots.
Perhaps Naruto finds a way to travel back in time and prevent Kushina's death in the first place. He could use his Sage Mode or some other special ability to manipulate time. And then, by changing the past, he effectively'revives' her in the present. In the Naruto universe, there are all kinds of crazy powers, so time - travel isn't completely out of the question.