Lumiya is a seriously watered-down Emperor's Hand. Lumiya would not be able to take anyone on the Jedi Council. She may give Corran a headache, but still would lose easily. When Luke fought her, he had to deal with the possibilty of collatoral damage to civilians thus imparing his fighting ability.
For the record I never said Kyp was better than Luke with a lightsaber or the Force. I meant to say that Kyp is an excellent swordsman and abnormally strong in the Force. In "Dark Journey" Kyp was able to dispell FL by narrowing his eyes. That's incredibly strong and Lumiya definitely would not be able to defeat Kyp.
Lumiya could not comfortably defeat anyone on the Jedi Council, I don't think. She posed a viable threat to Luke Skywalker when he was still developing his skills shortly after Return of the Jedi.
After all, she is part cyborg and received training from the Emperor more as a spy and assassin rather than a warrior.