I don't see this as that tough of a decision, whether your WITH the parents' decision, or against it. It seems pretty simple to me.
She has the mentality of a 3 month old, and, supposedly, will ALWAYS have the mentality of a 3 month old.
Her body would, naturally, mature. She'd go through puberty, which, in biological terms, is only really good for a person if he/she wants to have children.
Ashley, with the mentality of someone FAR younger than her age, would NOT be able to take care of anything, let alone her own child.
So, going through puberty serves no point in enhancing the quality of Ashley's life.
Stunting her growth ALSO allows her to always be able to play/interact with other children who have a mentality close to her "perpetual mentality" without having the body of a 24 year old, and thus being less intimidating to children, and easier to get along with.
For Ashely's sake, AND her parents' sake, keeping her small will help TREMENDOUSLY with caring for her and giving her what she needs. She can't go to school, because 3 month old children DON'T go to school, and she wouldn't be able to do anything at all if she were to go to school, besides be a bother to the teachers.
Mentally handicapped children often have different classes directed at helping them with understanding and the "special care" that they require. Ashley's special care is 24/7, as is an infant's. She needs her parents all the time, for everything.
I see no controversy here. She's lost nothing at all. She wouldn't even KNOW that her body was changing, or that she could walk, talk, tie her own shoes, etc, because her brain can't process it.
Kudos to the parents and to the technology and research that let such a procedure occur.
Slippery Slope? Yeah, maybe, but can't we tackle that when it comes, and for now agree that this was the best course of action for this child?