I really don't understand Morgana. I mean, yeah, she's evil, twisted, and a tad insane, but I've always thought she was quite clever.
Case in point; she masterminds what she obviously assumes to be a great plan involving Princess Mithian, Arthur, and a fellow loony called Odin, when really all she had to do was get Arthur out of Camelot so that she could blast him into oblivion.
I mean, she did that almost immediately; there was no need for the other stuff. I'd give her advice if we weren't enemies, as clearly she needs help.
Not that she'd listen.