Here's how you can answer, depending on the situation:
If she is a student in Miami:
* Sí, ella es alumna en una escuela de Miami. (Yes, she is a student at a school in Miami.)
* Sí, estudia en una escuela de Miami. (Yes, she studies at a school in Miami.)
If she is not a student in Miami:
* No, ella no es alumna en una escuela de Miami. (No, she is not a student at a school in Miami.)
* No, ella no estudia en una escuela de Miami. (No, she does not study at a school in Miami.)
To make the answer more specific:
* Sí, ella es alumna de [nombre de la escuela] en Miami. (Yes, she is a student at [name of the school] in Miami.)
* No, ella es alumna de [nombre de la escuela] en [otra ciudad/país]. (No, she is a student at [name of the school] in [another city/country].)
Remember:
* alumna is the feminine form of "student."
* If you are unsure of the school's name, you can say "en una escuela" which translates to "at a school."