I guess the same way we un-brainwashed you --
No ay milagros - ¿no sabes nada, Chica?
No se - no puedo pensar para ti, Niña --
Ah...miracles happen all the time!
Brain washed according to who? Are you taking this child to prove that your belief is better than hers? If you truly care about the child, what does it matter what god she believes in? Allow the child to have her belief and how would that hurt you? Let your actions and your sincere concern for the child demonstrate the value of who and what you are?
"How do you teach a child who has suffered from trauma, abuse, neglect, who has been taught to seek comfort in god....how do you show them the truth? How do you do that without shattering their world?"
Um it sounds like their world has already been shattered. Now how do you heal it? No actually I think that's a suspicious question. A better question would be how do you develop it, make it grow? Well I think you let the child think for herself. Whatever she decides to believe or not believe she can do on her own.
But introduce her to an environment that would help her see in new perspectives, new ways of thinking, new ideas. Sort of like what Karl Popper had in mind of his Open Society. Show them that there are other ways of seeking comfort aside from the church. Maybe you can take the child to the museum (art and science, etc), watch different movies, and I mean different for example a person who just watches action movies all the time is depriving his or herself of the many other varieties of movies out there, Different kinds of music? Rock, classical (and not just Bach or Beethoven, like maybe say the experimental Steve Reich). Give them variety, give them alternatives.
Classes to play music. Dance classes where she can make friends(youth groups are not the only game in town to make friends)...etc
The same goes for intellectual pursuits. Its good to study different subjects, Some people just focus on one subject, so they want to be a computer programmer but they know nothing about the law saved what little they see on TV which can very much misinform them.
I answer this way cause I ask myself a question. This child's world is so narrow. How do I enlarge it?
"How do you do that without shattering their world?"
ha ha with my advice you'd be shattering their world... their narrow world...if you can call it a world, what's that a euphemism? it sounds too generous... more like a prison, give them a real world: rich, sophisticated, variegated... and full of possibilities...