Should I report my professor?

The dean excused her absence, so this isn't really just your professor. There's a lot of policy issue here that goes way above his head, which isn't really his fault. He could fail her, but that might not be kosher since the dean (his boss's boss) already approved her absence. Chances are that if it's midterm time, she's likely missing more than one midterm; all of which she'll have to make up. I think if she's taken the time to appeal all the way to the dean to get her absence approved, and actually got that absence approved, then she deserves to have the time. It's pretty hard to even get appointments with the deans at most colleges. My advice would be to focus on your own work, rather than focusing on whether this situation is fair or not. There's enough going on during midterms; you don't need to be thinking about all of this stuff too.