Exactly, light and dark are much closer than you may think. And for Kreia, who was almost a grey Sith, they may have being even closer. After all she says, in regard to the Force:
Interesting choice of quote. For two reasons. The Jedi Mantra, "There is no death, there is the force"
And as Yoda quote "The force is my Ally, and a powerful ally it is".
Indicates very slight differences given that angle
If you are to truly understand, then you will need the contrast, not adherence to a single ideal.
She obviously drew on the teachings of the Jedi and the Sith. So perhaps she actually followed that line in the Jedi Code, "There is no passion, there is serenity." Or at least to an extent.