Lucky, lucky, Eey. Narcissa/Lucius is my favourite canon couple and you certainly did them justice with your story.
While Narcissa is portrayed in canon (Harry's POV) as a stuck-up bitch, what also comes through is how ferocious she is in protecting her family. In addition, what is often not touched upon by other stories is that she is both a Slytherin and a Black.
Lucius should worship the ground she walks on and apparently he does after she shows him the lengths she'll go through to satisfy him. Excellent story!