She might become angry at first. Natsu is known for her fiery temper. So, she could lash out at the person who betrayed her, confronting them directly and demanding an explanation.
I'm not sure who exactly Natsu is just from 'natsu reads fanfiction'. It could be a normal person who just enjoys reading fan - made stories. Maybe it's a nickname for someone within a particular fan community.
Another idea for this fanfiction could be that they were both students at a very old and secret magic academy in the past. Zeref was an outcast because of her dark magic, but Natsu didn't care. He befriended her, and together they explored the secrets of the academy and the magic within it. However, their friendship was soon tested when the academy's elders discovered Zeref's true nature.
Their relationship could develop through shared battles. When they fight side by side against common enemies, they start to trust each other. For instance, in a fight against a group of dark mages, Natsu and the female demon realize that they complement each other's fighting styles. Natsu's brute force combined with the female demon's more strategic and stealthy attacks make them a powerful duo.
In the 'natsu went mia in war fanfiction', Natsu is presumably a central or important character. He could be a hero - type figure who was expected to play a significant role in the war. It's possible that he has some special abilities or traits that made his presence crucial. Since he went MIA, the whole story might be about his friends or allies trying to find him or dealing with the aftermath of his disappearance. It could also be that Natsu is a character with a complex backstory, and his going missing in action is a key event that will unfold and reveal more about his past, his relationships, and the overall world of the fanfiction.
A common theme could be friendship. Natsu and Gajeel have a complex relationship in the original series, and in fanfictions with a female Gajeel, exploring how she fits into that friendship dynamic can be interesting.
One common theme is friendship. They often start as just acquaintances or even rivals and then develop a deep friendship. Another theme is growth. Both characters, especially female Natsu, grow in terms of their powers and personalities. For example, in many fanfictions, female Natsu learns to control her new - found abilities better with Laxus' help.
A common theme could be friendship. Since they are both interesting characters from the same universe, many fanfictions might explore how they become friends despite their differences.
There could be a plotline where they get into trouble in a magical realm. They have to rely on each other to find their way out. Along the way, they face various magical creatures and obstacles, which test their friendship and loyalty towards each other.
Romance is also a big theme. Many fanfictions play around with the idea of a romantic relationship between female Natsu and Gray. They might have some cute moments like blushing or secretly caring for each other.