I hope you're right, but I highly doubt it. The damage that's been done cannot be undone except by much prayer and penance on the part of the 12 year old. But first she has to want to change, which is very unlikely, especially for an indoctrinated 12 year old.
While these things are true (i.e. prayer, wanting to change), it doesn't follow from the need of those things that it's "too late." That's terrible advice. Tell the parent that it's too late to save the kid and they'll just keep them in public school, all but ensuring their kid's demise.
What natural hope remains is in removing the kid from the problem, which is the godless environment that's introduced, legitimized, and reinforced the ideas the girl has picked up. Children are malleable. Less so as they get older, but still malleable.
It was not advice, nor could it have even been intended to be advice, rather, it is simple reality and it is based on personal experience.
Disturb the child's programming, and the family will have hell to pay - that is the way it works, that is the expectation. A 12 yo child who has had her mind perverted like that, can rip a family apart. I sincerely hope this case is different.
What should not
be expected, is that the brainwashing can be undone at all by anyone, except her. Were it possible that the brainwashing were to be undone, that would be the exception not the rule. That's just reality.