Well, it could be due to a powerful enemy attack during a fight in Wave. Maybe an enemy with a sharp weapon or some dangerous jutsu managed to strike Naruto's eye.
Well, one possible plot development could be that it makes her more determined. Losing an eye might be a turning point where she decides to train even harder to overcome her disability. Maybe she starts to focus more on her other senses, like Naruto in the original series focused on his sense of smell when his vision was blocked. It could also lead to some interesting interactions with her friends. They might be overly protective at first, but she would prove to them that she's still the same strong - willed person.
She would probably have an eye patch, which would give her a more rugged and battle - hardened look. Her overall expression might become more serious, as the loss of an eye is no small thing. The remaining eye would likely become more intense, as if it has to make up for the loss of the other one.
Sure did. Thor's loss of an eye is a key development that adds depth to his character and story arcs in the comics. It often symbolizes his growth and sacrifices.
There could be a fanfiction where Fem Naruto discovers a hidden side of Fem Kyuubi. Maybe Fem Kyuubi has some memories or powers that were locked away and Fem Naruto helps her unlock them. This could set off a chain of events that not only changes the relationship between them but also has a major impact on the entire ninja world as they face new threats and opportunities together.
There's also the possibility that it's an accidental injury caused by one of Naruto's friends during a training session gone wrong. For example, Sasuke could accidentally unleash a jutsu that hits Naruto's eye while they are sparring.