When Hayley Williams of Paramore hits the high note?

I was wondering about the way Hayley sings the high notes. Does she shout or use what the pros called the head voice? Or is it a mixed of both? Usually when a person teaches you how to sing high notes they usually let you hear what singing a high note sounds like and it does sound high, like the voice thins out but it's still rich with quality-- kinda opera-ish. But with Hayley, when she hits those amazing high notes, her voice somewhat still sounds the same, Idk how to explain it properly but like, it doesn't "thin out" or it doesn't sound like the traditional "high note" we hear. I dunno maybe something about that range, singing with the diaphragm, and the head voice thing.