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.
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.
One possible reason could be that Mirabel might have accidentally broken an important family heirloom. In the context of the Encanto family, their heirlooms are often tied to their magic and family identity. If she damaged something like that, Abuela, who is very protective of the family's traditions and magic, would likely punish her.
I'm not sure there are a lot of Orb Weaver Mirabel Madrigal fanfictions specifically. But it could be really interesting if it focuses on Mirabel's unique personality within the Madrigal family and how she might interact with an orb weaver concept. Maybe it could be a story where Mirabel discovers an orb weaver with magical powers that are related to the family's magic in some way. For example, the orb weaver's web could be a symbol of the family's interconnectedness that Mirabel has to figure out how to use to save the family's magic again.
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.
I'm not sure specifically as it could be any number of creative interpretations. It might be about a situation where Alma Madrigal blames Mirabel for something within the context of the fan - created story, perhaps related to the events or family dynamics in the Encanto universe.
At first, Mirabel might be shocked and confused. She would probably wonder why Abuela would do such a thing to her. She could spend her initial time in prison trying to figure out what she did wrong or if there was some mistake.
One possible reason could be a misunderstanding. Maybe Abuela saw Mirabel doing something that she misinterpreted as a threat to the family or the magic. For example, if Mirabel was exploring a forbidden area in the house where the magic was acting strangely, Abuela might have thought she was endangering the family's future and thus imprisoned her out of fear.