Yup. And you just can't get a really vibrant un-natural pink or blue by applying it to unbleached, naturally-colored hair.
(Which is a long way around of saying: it's xFenrir's hair, and she really can do whatever she wants with it. Even if it's not your thing. It's great that you like your wife's hair best the way it is! And I'm sure xFenrir will find someone who digs her style, if she hasn't already.)