How do I get my boss to come to work on time?

I work overnight shifts as a night auditor from 11pm-7am. She is the assistant manager and supposed to come in at 7am on tuesdays and thursdays. She has never once been on time to cover my shift. I have calculus at 8am, so I'd love to leave work on time. She usually gets here between 7:10-7:20. Last Tuesday, she didn't get here until 8:30. I thinkits likely due to the fact that she's salaried. Her perpetual tardiness is starting to affect my school work. I've conveyed to her that I have class, but she is still always late? Should I go above her to the general manager?