Mary Cain is very brave for coming out and saying what she did.
That said, I think it is clear that - like a lot of young women - her body was changing as she matured. That is the main reason she was no longer as competitive.
I want to ignore the whole doping issue because I think that is tangential and just focus on how the program criticized her for her weight. It was DEFINITELY abusive to treat her the way that they did. There is no excusing that. However, I think it is disingenuous for her to claim that they ruined her career ("I was the fastest until..."). They ruined her self-esteem and harmed her health, yes. Ruined her career? I don't think so. They were trying to prolong her career although it was in a nasty, unhealthy way no one should experience and I applaud her for calling them out on it.
I would like to know what she thinks they should have done instead - send her home and tell her the unpleasant truth that her career is over because her body isn't the right type for her chosen sport? It would have probably been best for her physically, but not sure that would be too great mentally. They did what coaches of all great athletes do, push her in the right direction until she succeeded or gave up. When dealing with adolescents in particular it's a nasty profession. She suggests hiring psychologists. I am not sure that is up to the coaches to do. What other suggestions does she have other than not shaming athletes in public (which is despicable)?