She finally messed with Sasquatch one too many times.
Although the latter experiment had to be stopped after only a few days due to an "unexpected lack of mummification" (here taken to mean, "It started to rot"), the natron experiment eventually yielded what the scientists had been looking for: a completely mummified leg, as well as an unexpected opportunity to discover what it's like to never sleep again.
They could never listen to ZZ Top the same way again.
Along with a blow-by-blow photographic record of what the mummification process looks like, the experiment concluded that the speed at which human remains mummify depends on factors such as temperature, humidity, and acidity. They even noted that the experiment would have finished quicker if it had been done in a desert environment. However, their bosses presumably pointed out that they'd already flirted with a horror-movie-esque death by creating their own mummy, and doing so in Egypt might have tempted the gods into unleashing some righteous karmic justice.