Pretty much the same thing happened during my final year. If you form an opinion it is best to keep it to yourself in certain situations. I too ended up having to appeal a biased grade however I went straight to the university president since my classes were capstones with the department chair. So in my last year I ended up taking her up on the offer she made during orientation when she talked with everyone. To this day I still remember walking through those huge wooden doors and saying Ms. X I need to take you up on that offer.