Will failing one class kill my chances of getting into a good graduate school?

Is it too late for you to withdraw? You might want to look into that. If not, though, I don't think it'll be a dealbreaker. There's usually a place on the application where you can clarify any issues in your academic record. You can just explain that you wanted to stretch yourself, but you got in over your head despite your best efforts and the experience really reaffirmed that [chosen program] was what you were meant to do. They'll probably conclude that themselves if it's a total outlier compared to the rest of your record, but it helps to give your side of the story. (Alternatively, you could retake the class or at least take a similar elective that's more forgiving to non-science majors, but I don't think it's worth it if there's other stuff you need/want to take instead.)