Orbert, thanks for your reply. Yes, it's probably true more often than not (although I'm curious about the percentage). I see less woman at DT, but for example, half of the people I see at Paganfest (pagan metal festival with mostly heavier music than DT) are female.
And you have to admit in return that how it happened with your wife could well be the other way around. You see it in the world: so many men go for the mainstream/less loud music as well. It could've been her loving it and you not. Of course, we can look at the numbers with everything, but then again, I prefer to see each human as a person and not as a gender.
(Note: I don't mind people listening to mainstream music or if woman listen to heavy music or not, love 's for everyone! : p)