How difference about "may be not" and "may not be"

from: http://www.usingenglish.com/forum/ask-teacher/46869-may-not-may-not.html

[1] She may be not a student, ...
Meaning => True, she is not a student, she's a teacher, but she works just as hard as a student. She studies English at home on her own time.

[2] She may not be a student.
Meaning => There is a possibility that she is not a student.


Modal may, like modal must, is ambiguous between epistemic and deontic modality:

Deontic modality
Ex: She may go to school.
=> permission; e.g., she is allowed to go.

Negated
Ex: She may not go to school.
=> permission to go to school is denied.

Epistempic modality
Ex: She may be at school.
=> possibility;e.g., It is possible that she is at school.

Negated
Ex: She may not be at school.
=> There's a possibility that she is not at school.

Ex: She may be not at school, but ...
=> True, she is not at school, she's at home, but she's at home studying right now as if she were in school.

Does that help?

Thanks : vv0510_vn who posted this question and Casiopea who explained this question.