Disclaimer: I know nothing about prions.

I think there's a mistake in the article, her website goes into more detail:

https://soutien-a-emilie0.webnode.fr/lhistoire/ (gtranslate)

> Emilie is therefore working that day on samples of mice infected with strains of human prions. It is important to stress here that these were human strains and not animal strains, the species barrier no longer protecting, the infectivity of the pathogens handled by Emilie was therefore total.