Natalie was an artificially created person- made by Glaber- who was abandoned when he moved. She was later "edited" by the mammals to become a creature that was able to take down Camille.
She's very stiff and kind of a blank-slate- most people find her off-putting and stand-offish. She's friends with Camille (though it's not a very deep relationship), and Camille has a crush on her. Camille isn't aware of her past affiliation with Glaber, and Natalie planned to keep it that way.