I received a C+ one semester in my Italian Cinema class, yet the work I did actually got me an A.
I received a C+ because I missed somewhere between 6-9 classes. The format of the class was simple... we watched an Italian film every other week, and on class days in between those movies we discussed the films. I never showed up to the nights where we would watch the films because I used to like watching them on my own. I did all the work, which included a 10-page paper written in Italian and an oral presentation in Italian about our favorite Neorealism films, plus two or three exams.
My work earned me an A. My absences dropped me down to a C+. I went to her after the semester and complained and she told me I should have attended class more often. Even after showing her that my work was better than half the kids who did show up, she still didn't care at all. It wasn't like a lecture class where I was missing vital lectures. I was still watching the films and doing the work about them. It still pisses me off to this day. Then again, I get the last laugh... because the next semester, her work visa expired and she was deported back to Italy.
And that's one example of why sometimes college is a great big pile of bullshit. On my transcript, it says C+... and yet I had a perfect semester in the class and did fantastic work. But because I physically didn't show up to the building for some classes, my grade was dropped.
At the beginning of the semester, did your professor state that class attendance will go towards your grade? If so, then that is her grading policy and you were obligated to attend those classes. If you knew that not going to class on those days affected your grade, then you shouldn't complain.