If the fanfiction incorporated the family's magic in new and creative ways, some characters might be delighted. For example, if it showed Mirabel having a new form of magic related to her ability to bring the family together, the family members might see it as a positive expansion of their story. However, some might be skeptical. Abuela Alma might question if it goes against the family's established magic traditions.
The younger characters in Encanto like Antonio would be excited. He loves stories and new ideas, so Mirabel fanfiction would be like a new adventure for him. He might want to share it with his animal friends. And Dolores, with her ability to hear everything, might already know about the fanfiction. She could be either intrigued or a bit worried depending on how the fanfiction is being received by the rest of the village. If it's causing a stir, she might be concerned about the family's reputation, but if it's positive, she would likely be quietly supportive.
It could make them realize how much they've taken her for granted. They might have been so focused on their gifts and their own roles that they didn't notice Mirabel's pain.
She might be heartbroken at first. After all, being kicked out by her own abuela is a big blow. But then she could become determined to prove herself. So she might set out to find a way to show that she is an important part of the family even without a magical gift.
Mirabel could use her wits. Since she has a strong will and determination, she might find a weak point in the place of imprisonment. For example, if it's a locked room, she could search for a hidden key or figure out how to pick the lock.
Perhaps Abuela believes that Mirabel's presence without a gift is somehow jinxing the family's magic. In the fanfiction, she might think that by imprisoning Mirabel, she can stop the negative effects she thinks Mirabel is causing. This could be related to some superstitious beliefs within the Encanto about the balance of magic and the role of each family member.
Some might be amused. It's a new and different take on their story, so they could find it fun.
Perhaps she tries to understand Abuela's perspective. Mirabel is a kind - hearted girl, and she may think that there is a reason behind Abuela's actions. So she might try to see things from Abuela's point of view while still feeling the pain of the punishment.
Mirabel might be initially shocked and heartbroken. She loves her family and the village, so being banished would be a huge blow. She could cry and try to plead with Abuela to change her mind.
Maybe she feels left out in the family. In the Encanto story, Mirabel is the odd one out not having a special gift. This could make her feel so alone and unwanted that she decides to run away.
It could be someone who is jealous of Mirabel's potential. Maybe a relative who feels that Mirabel's new - found importance in the family (even if she doesn't fully realize it yet) threatens their own status. For instance, a cousin who was once favored but now sees Mirabel as a threat.