This has polarized opinion with disabled rights campaigners saying it is more for the carers benefit and starts the slippery slope to eugenics. On the parents side they insist it makes her more comfortable and retains enjoyment opportunities for her that increased size would take away. I raise this here as the 'treatment' is now being taken up by other families, albeit on a small scale.
My own position on this isn't simple. We've had a profoundly disabled child who grew up into an adult. I'm fairly sure we wouldn't have gone down this road even if it had been available or relevant. That isn't because I feel it's intrinsically wrong. I think this 'treatment' probably went too far but it really is complicated, and it worries me that many committed people seem willing to take up definitive positions so quickly on almost partisan grounds.
The surgery involved was major, involving breast removal and a hysterectomy, followed by hormone treatment. There are risks with the surgery itself (we did not do some operations on our son precicely because of the anaesthetic risk) - and there are ethical issues about some of the surgery (as our child was a boy rather than a girl, much of this would not have applied). I understand and have a lot of empathy for the 'drift towards eugenics' arguements (in my experience there is more of an acceptance that disabled people are less 'worthy' of expensive intervention than normal people, even among medics, and I will fight this forever). On the other hand(s) this is after all, just another medical procedure, and I don't feel it should be discounted on the grounds of being 'unnatural' - all medical treatment is 'unnatural'. I have to say that I find the sentimental arguments about keeping her childlike difficult to take and in particular find the 'pillow angel' comments a little sickening.
On the other hand(s) I have real sympathy with the parents reasoning. She would be spared considerable discomfort (lying down and period pain), would not risk pregnancy (presumably from abuse) but most importantly would be able to do things and be cared for better while small (this may be the fault of society making things inaccessible, but society does make things inaccessible and that's real even if it's wrong.)
I'm not going through all the arguments here as I believe it's too complicated to take an across the board stance - each person involved will be different. I raise it as an extreme case that is likely to get more visible in the future.
Our own son would not have been able to have decided any of this for himself and I would have fought tooth and nail for any treatment I believed would have made his quality of life better. He was his own person and had the right to grow up, but he also had the right to a comfortable existence. We agonized greatly over his fundal plication (which closed off his stomach to prevent reflux but also meant he couldn't enjoy food - he was then fed directly) and only agreed to it when the choking risks became life threatening. The decisions on these things need to be taken looking at the person holistically and putting yourself in their position if they can't decide themselves - taking overall, snap judgements on this isn't helpful.
I had hoped that this could only have happened in America, but I understand a few people in this country have also had the 'treatment' now. Read around this if interested and don't make up your own mind - you will be wrong in many cases if you do. What is right for the individual is what matters, not the party line.