Anyway if you did, (SPOILER)In the back entrance of blighttown, the one taken through New Londo, there's an undead dragon guarding a Dragon Crest Shield, this thing greatly reduces fire damage, it is your friend in this fight. Dat ho mainly gets you with fire damage so you are going to want that, and to unequip your armor because it won't really be helping you against the fire. Other than that, stay back, to engage her in a corner because if she pukes at you, you're smurfed. Dodge back and forth not left and right, and when you want to hit her, get all up in her face.