Easy way is to get yourself in a standard game on insane then get someone on casual to hammer of dawn on the boss. Casual player only needs to hit it once and the fights over.
If things do get sticky you can hide around the back of the lift where you come up, enemies wont come at you because of spawn protection and the cover there is indestructible. It is also a good position to shoot off the enemy hooksas its where they scale
Try doing it by yourself. The way I did it was I stayed in cover while "spotting" her and letting the AI do all the work. All I had to do was use the Hammer of Dawn. I don't think there was no more than 4 Theron guards through the whole process. "Spot" them
too. You will be surprised how easy it is.