That's kinda the million dollar question. Faeries don't have souls. Mantels generally overwrite the holder's personality. But not necessarily. So is Molly human? Has her soul been destroyed?
Or it is a meaningless question because it depends on how you define human in a magical world were humans can transform in countless ways with all intermediates.
Biologically she is human. Mab can breed with humans and get fertile offspring. Does a soul make you human? Apparently not if a human can loose it.
So in this case I would say it is not about a definition of human something different groups in the dresdenverse probably can not agree on anyway but it is about acceptance and self identification.
Does she see herself as human?
Do other humans see her as human?
Do non humans see her as human?
If all three is yes then she is human. Otherwise it is debatable.