I think the accepted answer is not quite right, based on having read most of Oriah Mountain Dreamer's books a number of years ago -- so I can't recall which books contained what, but...
When she says faithless, she doesn't mean susceptible to pressure, but really faithless --
Edit: As per @Spagirl's comment below, I misunderstood her answer and am fixing that now.
By 'faithless', OMD does indeed mean what the quote says: willingness to disappoint another and be accused of betrayal to be true to one's soul. And it goes beyond that as well. Mountain Dreamer's laudatory take on faithlessness means being willing to break vows, willing to go against one's own convictions and values. Both the OP and @Spagirl in the answer above talk about being true to oneself, but Oriah Mountain Dreamer is not a moralist, she's a real spiritual daredevil. So, yes, she is talking about being true to oneself, but not like sticking to your principles. Mountain Dreamer's version of being true to herself is having the guts to follow her spiritual path to genuinely scary places.
I highly recommend her non-bestselling first book, Confessions of a Spiritual Thrillseeker: Medicine Teachings from the Grandmothers. The faithlessness quote is meant to be challenging, like the Nietzsche quote: “A very popular error: having the courage of one's convictions—? Rather it is a matter of having the courage for an attack on one's convictions.” Unlike Nietzsche, Mountain Dreamer doesn't have a philology professor job to support her radical independence, so I think her work may be colored by its market niche of new age self help, but what she's offering is not tepid self-actualization.