Please. Hundreds on this board readily decried German Fernandez for not going pro out of high school. While he was still running at Oklahoma State, there were threads every few weeks about how Dave Smith had ''ruined'' his running (which is ridiculous). Now, I don't agree with either of those points at all, but it seems probable to me that Mary Cain would have received a great deal of criticism for NOT having gone pro if she struggled at all in the NCAA. People would've gone on about how she squandered her talent, how NCAA athletes race too often, that she could have thrived with private coaching and Nike resources.
Of course, hindsight is 20/20, and so many people who post here relish in criticizing elite runners. The NCAA system is great for some (maybe even most), but Mary Cain was accomplished enough by the end of high school that going pro was a sensible decision. One might have said (and many did say!) that racing in the NCAA would've been a waste of her time, based on the level she was running at. Who could blame her for wanting to optimize her running by limiting her external distractions? A pro athlete has access to resources that no NCAA athlete does, and can set their racing schedule as they please with no obligations to a team or university - not to mention, they can race against superior competition.
At any rate, in my mind, the most compelling reason for Mary to compete in the NCAA would have been to receive an elite education. If I recall correctly, she was a strong student in high school, and I see no reason why she wouldn't have thrived at, say, Princeton or Stanford, both of which are excellent places to compete for. However, she made a reasonable choice to pursue professional athletics, an option which naturally has a limited shelf life. She's had her share of struggles the past year and a half, but she's just 19 years old - which, for the record, makes threads insisting that she's done running well all the more absurd. Hopefully, and there is still plenty of time for this, she will bounce back from her difficulties all the stronger. Meanwhile, the basement trolls like the OP (who think they are brave or intelligent or insightful for pointing out her struggles with dumb explanations) will still have accomplished less than Mary. Good luck to her.