I've seen it pop up from injury as well as just suddenly, likely from something genetically not matching up how it should. I don't keep them and absolutely won't breed them, so I don't know if it's inherited or not in those.
I did have a quail I eggtopsied that had horrendous crossing even before it hatched, likely why it didn't hatch, but I think that was incubator issues, since I did quite a bit wrong by accident in that batch.
I would let her keep growing until her beak gets worse (it might or it might not), just know she won't be as plump as the boys her age because she isn't eating as well. It would be easier if it was both top and bottom beak that was crooked since they would still line up, but I would keep an eye on it