My piano teacher has told me not to learn G8 pieces even though I'm good enough, because she doesn't want to do it yet. But I thought this one was fantastic, so I'm learning it.

Anyhoo, the problem is, it has some scale passages that are sometimes chromatic and sometimes aren't, and I can't help but use the chromatic scale fingering even when it isn't appropriate! How do you get over something like that...

Not only have scales not made me happy, they have made my fingering wrong! A curse upon scales!

.... first you look at it & work out where the tones & semitones occur. Then you play it slowly trying different fingerings until you find one that works best. And then you practise it slowly always using the same fingering until the fingering pattern & notes are consistently 100% accurate. And when you can do that then you can gradually up the speed.