^ easy, use toan or goro attack her up close,when her shield is down, quickly change to ruby to shoot fire at her, when she's back on the shield, repeat the toan/goro part and repeat that until she's defeated. I will command that you MUST have stamina potion on any of those 3 the whole time. If you don't have that when she used a crystal, you can be frozen for a short time. This boss is one the most challenging boss for my mom than she've ever faced a few years ago. LOL, it took her millions of times, while it only took me maybe 5 times or so.
![Laugh :^O :^O](https://cdn.statically.io/img/www.ignboards.com/styles/ign/ign/smilies/classic/laugh.gif)
If you have any questions, feel free to ask on this board. I don't have insider yet, but I will around Nov. or Dec.
EDIT: to change your element, press start, then go to weapons. There you should see elements and choose fire. Hope that helps, I've been playing this game for years, and I love it! Hope for a Dark Cloud 3.
EDIT: Maybe if you tell me what your weapons' fire, ice, wind, thunder, and holy levels are I can help with that also.