I visited her on Monday and while I did not sleep I did exit the citadel and return later. Her HP were still at the level I left her with. A mage with blood and elemental magic over 50 can spawn skeletons to act as a diversion while you come around behind her and use the ember staff. Leave the citadel and use a small shelter on the platform for rest and eitr regen. Re-enter and repeat. Skeletons do a good job and will take out even seekers at that BM level.