Gabi is still alive in the AOT manga. Her fate was determined by the plot and the author's choices, and death wasn't one of them for her in this particular storyline.
One popular AOT Female Eren fanfic is 'The New Path of Eren'. It offers a fresh take on Eren's character from a female perspective, exploring her relationships within the Survey Corps in a really engaging way.
AOT Female Eren fanfic is special because it offers a different view of the story. By making Eren female, it can change the dynamics of relationships. For example, her interactions with Levi or Armin might be different in terms of how society in the AOT world views gender roles.
Eventually, Eren might start to investigate the reasons behind Mikasa's betrayal. If he discovers that there are more complex factors at play, like she was forced or there was a misunderstanding, he could feel a mix of guilt for his initial reaction and relief that their relationship wasn't as broken as he thought. However, if he finds out that she truly betrayed him out of her own will, he might become even more determined to carry out his plans, whatever they are, without her.
Some fans are heartbroken. Eren is a very popular character, and his death can be a huge emotional blow. They might write comments expressing their sadness and disappointment.
For Eren, he could start off as a bit of a rebel in high school. Maybe he's always getting into trouble for questioning the school's rules. But as he spends more time with Mikasa, he starts to see the importance of following some rules and also becomes more empathetic. Mikasa, on the other hand, can be developed as the quiet, studious type who slowly comes out of her shell because of Eren's influence.