I made the mistake of googling the possible problems with bottom surgery and I think you need to be REALLY motivated to go through it. And you have to take care of it forever, because lack of care can lead to death.
So, I wouldn't push a minor into it without serious considerations. As the author says, SRS is life-threatening and you have to deal with this choice for the rest of your life.
I'm not going to say they shouldn't do it, but I'm on the mother's side here. Do it for yourself, only if it's unbearable to not do it, be informed of all the consequences and challenges you're going to face. Especially true for a minor. And be aware that while you'll be a woman in external appearance, as you always have been in your feelings, your body will still be fundamentally the same. You can't change your chromosomes.
But I hear that for some people, they couldn't bear to live without it. So, if they have to...
Again, I'm not sure why the author didn't mention puberty blockers (I should probably look at the previous chapters more closely, because it was MTL up to 6), maybe because it was not in line with the plot they want, but that's probably what Rinko should have done.