Without details, it could easily be either side in the wrong here. It could easily be both.
But couldn’t she just retake the class at some point?
However, I would like to add that it sounds like a spoiled brat not getting what she wanted rather than a vindictive teacher. JMO.
Some schools don’t permit you to retake a class for credit, or average the grades, etc. In any event her claim that one C+ ruined her life seems overstated.
Who knows what happened, the lawsuit is outrageous but please, people don’t remember lots of college students and professors being jerks? The amazing thing is running into a conservative professor.