All right, either there is a Death Eaters Spouses' Club...

...where Voldemort holds court from time to time, to tell the (mostly) ladies about his short and long term plans - and that's a serious plot bunny isn't it?
Or Narcissa is actually a Death Eater,a concept around which my mind has some difficulties wrapping itself.
Because in ch.2 of HBP, Bellatrix warns her sister against betraying Voldie's confidence. But it doesn't seem as if Bella had told Narcissa about Voldie's plan, no, the text says quite clearly that Voldie told Narcissa personally about his scheme.
Narcissa, a Death Eater? I'm so very unconvinced...