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.
It could be her mother. Mothers are often the ones who enforce discipline in the family. Her mother might feel disappointed in Mirabel for lying and give her a punishment to teach her a lesson.
She might lose the trust of her family members. In the Encanto family, trust is crucial. If Mirabel lies and is found out, her family may start to question her honesty in the future.
It could be Abuela Alma. Since Mirabel getting a gift would have a huge impact on the family, Abuela's reaction and her journey of accepting this new change in Mirabel could be a major part of the story.
In this fanfiction, Abula and Mirabel are likely characters within a particular fictional universe. Maybe they are part of a family or a community. Without more context, it's hard to say exactly who they are, but they must have some sort of relationship where Abula has the power or authority to kick Mirabel out.
Recovery and resilience are also important themes. Fanfictions usually show Mirabel gradually getting better from the concussion, which symbolizes her strength and ability to overcome difficulties. This can be very inspiring for readers, as it shows that even in a tough situation like having a concussion, one can bounce back and continue to grow.
There are quite a few out there. Some fanfictions might focus on the emotional aspect of Mirabel being adopted. Like how she initially feels like an outsider in her new family but then gradually finds her place. Others could be more about the plot - driven adventures that her adoption sets in motion. For instance, her adopted family might be part of a secret society and her presence there uncovers all sorts of secrets and mysteries that they have to face together.
Perhaps in the fanfiction, Mirabel gets a gift that allows her to see the true potential in each family member. So she uses this gift to encourage her family members to embrace their individuality more, which in turn strengthens the family bond. For example, she might show Luisa that there's more to her than just strength, and help her find a new passion.
You can start by searching on fanfiction platforms like Archive of Our Own or FanFiction.net. Just type in 'Mirabel adopted' in the search bar and see what comes up.