My thoughts on the blind kids scene
UGH! When I first watched that scene, I truly felt sick, I mean seriously what the? Why would kids willingly crawl on broken glass. But then I thought about it more and well, I'm not exactly sure if it happened but I took it metaphorically after over thinking it.
Lets say the doll represents May and the glass box is her 'safety bubble' if you like. The blind kids represent the present people in her life (Adam, Polly, etc). All her life May has lived in this safe bubble not interfering with other people but when she begins to come in contact with them, her bubble is burst (glass box broken) the people claw at her, tearing her apart, causing her to damage (kids crawling ripping apart the doll) thus making May to become unhinged, crazy, psychotic. May then tries to save herself (May holding the doll close) but it's too late, the damage has been done, she is broken (mentally).
I hope this makes sense.