Frankly, I always get confused with Russian short forms and diminutives ;-)
Is
Nadia the short form of
Nadezhda or the diminutive, or is it the other way round? Anyway, one is either the diminutive or the short form of the other one ;) And Nadège is the equivalent of
Nadezhda.
Although, the name
Nadia itself is also used in
France.
Another middle name I could imagine for Sévérine is
Maelle.