I dont know much about binding at all, but Avery/Elijah looks to be already kind of flat without the binder, it seems, so i don't know if it would be too much of an issue for it to be completely flat and without breathing issues? Again, ive never binded before so i dont really know how it works lol. Just speaking from theory
No matter how flat you are, anyone at her age would need to bind very tightly, especially using bandages, to get themselves flat like her, and achieving that would mean tight enough to definitely inhibit breathing a bit.
Do some research if you're interested. I'm just speaking from my experience and the experience of others like me.
This story is good, but there's just one thing that annoys me.
The author did absolutely no research on binding.
I mean, binding so tightly that the chest is completely flat makes it hard enough to breathe, that you would expect a few things, even from one who has been doing it from a young age:
1) You would expect binding breaks
2) You would expect there to be some repercussions (e.g. shortness of breath etc.) shown in the story
3) You would expect that the main character wouldn't be able to run around much, let alone sleep binding
4) What is going on with shortness of breath from a corset? Corsets are nothing like those stories of tightness that we hear depict them to be, and even if they were, there is no way that the main character would have any trouble with breathing in them. She's been binding for years, there's no way that this would be harder.
Well, that's my rant. Bind safely, kids.