IMO, this has to be about the most accurate take on the subject that I have read on this site yet. I somewhat disagree with your take on Mary Cain feeling trapped- I agree; she was not physically trapped. However, in a sense I truly do believe that the psychological issues that she was facing caused her to feel as though she truly was physically trapped (if that makes sense).
Finally someone says something about the parenting! She began working with Salazar (who already had a questionable reputation) in 2012 at her age 16. What parent wishing to give sound guidance to their child in their right mind believes that this is the best path for them? For a kid to begin working with a professional coach at age 16 and to turn pro at age 17 means that they have chosen to forego many valuable experiences in some of the most formative years of their life. To believe that this is their best path, the kid and the parents have to both believe that their running talent is so inherently valuable that the marginal benefits of running professionally versus as a collegiate athlete for a few years is worth more than the sum of experiences missed. This is a massive gamble with life-long consequences, and, in the case of most child prodigies (especially the female athletes) this is a gamble that will rarely pay off. The path that Mary Cain chose indicates to me massively misguided judgement on the part of those around her. If blame must be assessed, I think it needs to start with the parents.