As always, especially with medical issues, there is a LOT of nuance. Example:
Teenagers who are Jehovah's witnesses are allowed to refuse blood transfusion, every if it means dying. The courts will no longer grant a court order to override parents' wishes. This has been adjudicated enough that it's basically the law of the land. So here we have a situation where a teenager gets to make a decision that can be life threatening. Certainly even more impactful than transition surgery.
In a non-medical scenario, teenagers are often allowed significant input in deciding custody issues.
So these are two examples where teens are given serious input in decisions that affect them. So they aren't being treated as chattel or pets. They get to make serious decisions on their own behalf, to a certain extent.
The girl in this case wasn't 13; she was 15. That's a difference that matters. So, a lot depends on the testimony of the child, her maturity, state of mind, etc.
I would NEVER suggest that a psychologist get involved in cases like this. Any buyer's remorse can lead to a case like this. Same for the plastic surgeon. They'd be well advised to do their own psyche evaluation. They already do evaluations before doing plastic surgery on ADULTS; at least they should.
Also note that the surgery for minors is breast reduction (top surgery). And the stats are not real clear. One study says only about 110 done in four years. Another suggests about 1000 per year. Still a very small potato. Of interest is to note that teenage males who are not trans will opt for breast reduction surgery at a similar rate as trans females. So there's that.
And the REGRET rate is about 0.1% If that's accurate, then only about one person per year will have regrets. (0.1% of 1000 surgeries).
And finally, there is evidence that care for trans youth, including surgery, quite often leads to a significant improvement in quality of life; including less depression and less suicidal thinking.
So I'll stipulate that I'm not a fan. But like with abortion, it's not my business. The medical profession should work to establish some settled criteria as to how to evaluate teens for possible surgery.