Make sure it's morning (don't go at night)
make sure your clear all spawns in area
have meads for frost resist and health
have the best foods you can make.
Have the best 2 bows you can carry (one might break)
have 2-300 fire and/or poison arrows.
she telegraphs her attacks, pay attention. (you do not want to get hit)

Edit : bury your portal farther away from spawn