Gotta be circular breathing. It's an advanced technique where you're breathing in with your nose and out with your mouth at the same time. I could never get the hang of it
Usually your cheeks puff out when you circular breathe, I don't really notice them moving too much here so she might just have a killer lung capacity. The really high notes don't require too much air on clarinet either, so it's possible that's just one ridiculously huge breath.
Doreen Ketchens. The same channel transcribed another solo of hers from a stunning performance of House of the Rising Sun: https://www.youtube.com/watch?v=qCE9PaXvNxY
She also does lessons on her youtube channel demonstrating her growling technique: https://www.youtube.com/channel/UCjICXsF-fT27gB2997hOpgQ
