Not getting along with Spanish professor. Professor is condescending, and picks favorites. I feel I have enough evidence to do something
Others may disagree, but I think you should go over her head. When she's outright admitting that she plays favorites with the participation grade, her department should know. What they do with that information is hard to predict, but if such complaints become a pattern with this teacher, they (hopefully) have to do something about it. Plus, complaining now could put you on slightly firmer ground if she gives you a grade for the course that's low enough for you to want to challenge it.

If there's someone with a title like "Director of the Undergraduate Spanish Program," that's the person to complain to.