A unique thing I found out about the Butterfly/Moth gal was that apparently she just does a lot of damage to "Fullness", not nearly as much to health. Unfortunately, her mechanic makes her very hard to follow due to the way that the moves are set up, so it's still incredibly difficult even with one's HP being the only thing on their character due to D-Efficiency. Loss of movement or going against her gimmick still can do a lot of damage, I definitely recommend getting as much Intelligence as possible to avoid on her on a run.
But I hope this may help!