The demands were probably too much. Petro rides his athletes and most American divas can’t take that for too long. Her jumping is probably not coming along as she imagined and he is probably pushing more and more needing her points. Her thunder was stolen by a more talented freshman coming in and producing in crunch time. Shame because he can coach the field.
She probably had a fantasy about what college life and athletics was going to be like. That fantasy likely didn't materialize. She probably started feeling the pressure to train, and perform. She may have felt like she was not a big fish anymore and treated like any other athlete. I have seen this happen many times. Coaches that cater to the "I am special" athlete are not benefiting the athlete long term.