If you're finding the fight a bit rough, you can actually do some of the other quests in Lucalla that are intended for lv 12+. This may seem backwards, but in 2 play throughs so far, I have yet to enter the White Witch's home earlier than level 15.
By then the entire thing is a walk in the park.
I wouldn't recommend waiting that long, but you can certainly get another level or 2 under your belt to help make the fight easier.
