She's talking about green threads which is different from regular threading in python. Under nodejs/python style green threads only IO calls are concurrent to a single computation task. There is no parallelism under both styles of threading unless you count concurrent IO as parallel.

She is basically complaining about a pattern that was popularized by NodeJS and emulated in python by older libraries like gevent, twisted and tornado. Currently python3 uses keywords async/await as an API around the same concepts implemented in the older libraries.

This has nothing to do with GIL.