Is it in a child's best interest to testify before a Grand Jury with the proviso that any mistake could put the child away for years?
There is every reason to believe that this child 1) has been sexually abused
There is? Where is it? If there is, why haven't they arrested the abuser if they have the evidence?
and 2) has been brainwashed into believing she will roast in hell for eternity if she doesn’t do/say exactly what the FLDS leaders tell her to do/say, including allowing herself to be raped by whoever the leaders authorize to rape her.
LOL I don't know where to start. Does your religion believe that sinners roast in Hell for Eternity? I don't know what the FLDS believe but I do know that Joseph Smith certainly didn't believe or teach that, so that statement is probably wrong.
It is not the attorney’s job to work towards getting the girl sent back to her brainwashers and abusers for more brainwashing and abuse, just because the scared and brainwashed girl says that’s what she wants.
Then you obviously don't understand the purpose of a lawyer.
HUH?