Just don't get hit by the ice crystals. In that armor, I don't think you'd survive one hit. Even if you did, the slowing affect would probably do you in soon after.

My preferred method is to simply make a hiding spot at the edge/under the alter that I can duck into when she takes flight and hop out when she lands to jab her with the silver sword a few times. It goes pretty fast that way. Much faster than shooting a million arrows.

If she doesn't see you in the hole, she shouldn't shoot the ice crystals at you, but if she catches a glimpse, she'll likely destroy your cover, so it is best to have one or two backups.