They could had logically let her fear over being outted as a witch and her empathy and anger about Uther's persecution of magic turn into a mental break or the same paranoia he dealt with, but on the opposite end.
They could have let her keep her empathy and simply become the bad guy who was simply trying to do the right thing against an enemy that they felt required drastic measures
Either we see magic users using light magic and being wrongfully persecuted, or we see dark magic users who are already in the "fuck it...it's illegal anyway, so I'll do what I want." There is really only one vague instance of someone starting to shift from white to murky gray...and I'd argue that had a lot less to do with magic than loneliness and class
But yeah...the ultimate eyeroll is when Morgana finally takes control of the castle and turns the crossbows on the people because "the people won't accept me if I don't get the knights on my side, and this is apparently the best way to pressure them."
This from the woman who, multiple times, was willing to sacrifice herself for children and servants...both those she knew and those she barely had heard of, simply because it was the right thing to do only a year before