I did pretty much the exact same thing as King Counter. I died like, 7 times trying to do the cauldron thing, but the fireballs, or whatever, always missed, or I couldn't get to her. So I just hit her enough, and she finally lost all her health....but she didn't die. I was pissed, because I didn't want to do it all for nothing, so I just decided to go to the cauldron. I put a couple of firas in it, poof, dead. It takes a long time, but it was the only way I could beat the stupid thing.