Kakashi would likely be amused by the whole situation. He might give Naruto some tips on how to blend in better as a girl, using his own knowledge of disguise techniques. Iruka would be more concerned about the reasons behind Naruto dressing as a girl and would make sure Naruto is comfortable with it. He would also be there to support Naruto if any of the other villagers had a negative reaction.
Some of the male characters might be a bit flustered around Naruto as a girl. For example, Kiba might act differently, not quite sure how to interact with her in this new form. Hinata, on the other hand, could become even more shy. She already had a crush on Naruto as a boy, and now with Naruto as a girl, her feelings could be even more complex. The Akatsuki members, if they were to encounter Naruto in her new form, might underestimate her at first. But Naruto, with her indomitable spirit, would soon show them that she's still a force to be reckoned with, regardless of gender. And the reactions of the characters would not only be about how they see Naruto, but also how Naruto's new form affects the power dynamics and relationships within the Naruto universe.
Well, the other students in Gryffindor would likely be a bit taken aback at first. But then, knowing Hermione's intelligence and her tendency to be different, they would probably accept it. They might be curious about how she's going to manage to keep up the charade. The Hufflepuffs would be generally kind and understanding, perhaps even offering to help her if she needs it. The Ravenclaws would be intrigued by the idea and might study her transformation from a more academic perspective. The Slytherins, as a whole, would be more likely to try and use her disguise against her, either by blackmailing her or trying to expose her in a way that would cause her and her friends embarrassment.
Sasuke might be extremely suspicious. He has a long - standing relationship with Orochimaru, and this sudden change would make him wonder if it's a new trick. He would keep a close eye on her to see if she's still the same threat.
All Might would probably be very supportive. He's always been about the spirit of heroism, not gender. He'd encourage Izuku (as a girl) to keep training hard. Bakugo might initially be shocked and then try to act all tough, but deep down he might be a bit confused about his feelings towards her. Ochaco would be excited to have another girl around and might become even closer friends with Izuku.
Some characters might be very surprised at first. For example, Asuna could be initially shocked but then become very protective of Kirito as a girl. Klein might make some teasing remarks but still be a good friend. And the villains might see her as an easier target or a new kind of threat depending on how they view female characters in general.
Sakura might be initially shocked and then start laughing uncontrollably. She would probably tease Naruto about it for a while. Sasuke, on the other hand, would likely just give a slightly raised eyebrow and then act as if it's not a big deal, but deep down he might be a bit amused. Kakashi would probably make a dry joke about it.
Sasuke would be extremely suspicious. He has always seen Naruto as his rival and a symbol of the village's hope. If Naruto starts acting like Pein, Sasuke would think it's some kind of trick at first. He might even be ready to fight Naruto to figure out what's really going on.
Sakura might be initially shocked but then she would be determined to help Naruto find out what's wrong. She could start researching in the hospital's library for any medical or historical records related to such a phenomenon.
Jiraiya would have a very interesting reaction. Since he's a bit of a pervert in the series, he would have to really adjust his behavior. He might also see this as an opportunity to study the differences in chakra and fighting styles between male and female ninjas while also trying to guide Naruto in this new form.
The other characters' reactions would be diverse. Bakugo might initially be very confused and maybe even mock Midoriya a bit, but deep down he'd still see her as a rival. Uraraka would probably be very empathetic and quickly become a good friend to Midoriya in her new form, helping her with things like getting used to the new body. And All Might would be very supportive, seeing it as just another obstacle Midoriya has to overcome in her journey to become a great hero.