I'ts a double battle and the field is super heated. It weakens Water moves by half (iirc) and powers up Fire moves. Some Fire moves actually ignite the field, which then causes it to damage non-fire types similar to weather damage. When it's ignited, Water moves that touch the field (like Surf) causes steam to rise, lowering the accuracy of all active Pokemon. She has HP Ice on at least her Volcarona, which made Noivern a liability at times. A lot of her Pokemon carry a lot of coverage moves too, so don't expect Fire spam. I think this is the only Fire gym where I have to not recommend the use of Water types. The field weakens them considerably, and she has a lot of Super Effective options to use against them. But if you have Rain I would go for it, it keeps her Pokemon weakened and keep the field from catching fire as well. I had to use Sandstorm, which also keeps the field from igniting, and really made Sandslahs the MVP for being able to take out the most Pokemon on his own. In this case, I believe it was two (EQ only takes out half her team, the third of which won't come out until the end). Actually started training a Houndoom by the end of it, and Flash Fire bough me a few turns to heal other members, so thank goodness for that.