Without knowing the details of who told the court what, to evaluate what circumstances the court looked at, we can't possibly opine on any chances on getting custody back.

Her first step would be to consult with her attorney - or hire one if she doesn't already have one. Now that she's LOST custody, it's not going to be a "do it yourself" case. Loosing custody means that the court has found her to be unfit. She'd need to consult with her attorney to address/fix whatever elements the court laid out as being problematic, THEN she'd need to prove to the court's satisfaction that switching custody back would be in the child's best interest. The longer it takes for her to fix whatever problems the court found, the less chance that the court will shake up the child's life again, by changing custody (courts don't like to make ping pong balls out of children - so mom needs to move quickly and follow the advice of her attorney religiously).