I should also add that in the second part of the battle with just Maris, your strategy should be completely different. Just keep hitting her over and over again. Her only good attacks are ranged, so if you stay up close, she can't damage you much. Use Vexxtal because the green damaging aura that it creates will help you track Maris when she goes invisible.
I just beat her on Sith Master using this strategy, and all I did was spam the X button until my thumb hurt haha. She hardly damaged me at all.