Rossweise and her redhead sister are both literal dragons.
They are natural born dragons. There are two kind of dragons in this world: viviparous, natural born between a couple through breeding and oviparous, dragons born from eggs from one single dragon.
The reason why there are fewer dragons and more humans is that dragons consider things like romantic love and seeing the opposite genre as cute, pretty or beautiful as a weakness. They are ruled by power and a meritocratic society.
Additionally when a dragon is pregnant she is defenseless for several months and their partners too in a way because they have to provide for both and protect her, meaning he is vulnerable too.
Opposite to this, laying an egg also requires a lot of energy but it's a safer bet however the libido is much meager in those individuals plus the prejudice against romantic and emotional feelings I mentioned before.