My boss requested me to work much more time than my suggestion

I offered to work as little as I could during summer vacation in order to ensure the time to study for the entrance examination of graduate school.
But, after I submitted my schedule form to her, she sent e-mail to me. The content is that she wants me to work another 11 days!
Though I don't know whether she passed an entrance examination of graduate school, she should know how hard it is to pass the examination.