Did Emilie Sagee ever really exist?

While searching for something entirely different on youtube, I stumbled on the story of Emilie Sagee.
It made me curious to know more. The story told of quite a few witnesses, but didn’t name them, quote them or give credit to any sources of information. I tried google searching, but everything I found told the very same story, either in the exact same words, or darn close to.

Does anyone know if there exists any reliable record that this woman lived?