Of course you can do beauty training in your spare time! People indulge their hobbies and interests, and do sports, photography, music, languages in addition to further education, so why not you?
Would she complain about students having part-tine jobs, as many do? There's semi-professional sportsmen and women that work other jobs around competing; is that greedy, or committed? Did she give a reason for her comment; maybe she's a bit envious of your uni education?