Since mi tía can be replace by the subject pronoun for the third person singular in feminine form, which is ella, then we must choose the conjugation of the verb regresar that matches this person as well. From the option, regresa is the conjugation of the verb regresar that matches the third person singular in the simple present tense. This tense is being to describe something that is going to happen in the near future. So:
¿Cuando regresa mi tía de México? (When does my aunt come back from Mexico?)
Explanation: Because if María says this she would be recognizing that Juan is more intelligent than her and always people believe that they are smarter than other people.
