Nathalie feels like she is getting replaced by a different character in every season.
I think you can separate it into 2 parts really. Pre and post Jubilation Nathalie. (I think it was Jubilation, I could be wrong)
From the beginning she is a cold, calculating, amoral wan who serves the Agrestes. It expands to show she has a thing for Gabriel in S2. She basically maintains that course up until her previously dying 115lbs self overpowers a 6 1/2' tall man and spells how how her motivation has been rewritten.
Then no one acts on this information until the finalé.
It really does highlight how S5 was just trying to wrap up everything for a series finalé.












