I actually just stumbled onto a way to completely sweep her team. I had no intention of using the method, and I really had no idea it was even a thing.
I very seldomly defeat a leader on the first try, just because I go into each battle completely blind as to what the Pokemon and field effects are. Same was with Charlotte, and I quickly found out after a single Eruption/Confuse Ray combo from that Typhlosion and Ninetales that I would have to negate the field effects somehow. It was kind of like Corey, who I had no chance of beating without using Gust to get rid of the poison field.
I remembered that I had a Rain Dance TM, and that seemed like the obvious way to get a bit more odds in my favor. But my only main-team Pokemon that could learn it was Genar, which was actually good since I was sure that, at level 69, my Gengar would outspeed everything and get it up. So I led with both it and my Noivern, hoping to use Air Slash on the Ninetales to get a lucky finch to avoid the Confuse Ray. Unfortunately the Typhlosion was still faster than Gengar (was it scarfed? either that or my IVs are terrible), but it went for Hidden Power on Noivern instead of Eruption (I think it was Rock maybe, not enough damage for Ice).
So my Gengar survives to get a Rain Dance up... and then the rainbow. I didn't know that was a thing at all, but I was just glad that the fire-field was gone. Then I thought "..you know, Boomburst would be awesome right now, since Gengar is immue." So I used Boomburst with Noivern, and the rainbow STRENGTHED the attack! So I had a Noivern that outsped everything and had a boosted Boomburst that Gengar was completely immune to. So I just spammed Boomburst in conjunction with Shadow Ball/Dark Pulse, and the whole thing was over before I knew it.
I've never stumbled upon victory in any scenario in Reborn, but this was pretty neat to me.