Zariah was smart to use Morgan's water against her; not expecting the electricity running down towards her she tried to quickly drop the spell, get it away from her hands. While the full force of the lightning did not reach her, enough did for her to make a hiss of pain and stumble, her body feeling as if it were vibrating from the force running through it.
It seemed she was not going to succeed here on magical means (probably to be expected, since she was fighting the Archmage) - but well, a part of combat was expecting the unexpected, right?
Perhaps it was underhanded but in a last ditch effort, probably an admission that she was not going to win this through magical ability, Morgan flipped a knife out of her belt and ducking forward until she could, she aimed to shoot it towards Zariah's neck with her telekinesis, the blade stopping just short of making a cut.