I didn't watch either race at all. However, I'll be the first to disagree with the suggestion for her to "run for a college team" first. Sorry if my post sounds a bit caustic, but the "running for a college team" argument has been beaten to death here.
1) Since she's 18, I don't see how she COULD have run for a college team before this race, unless you count a few weeks of training as "running for a college team".
2) Just because some runners have success in college does NOT mean that runners as a whole will benefit. Just off the top of my head, Fernandez was effectively ruined in college, Webb didn't do very well in college, Derrick stagnated for some time after his Freshman year, Jager left in the middle of college, etc.
This has been brought up many times before. Cain as a female high school phenom is well beyond all but a few in US history. She's beyond Verzbicas, Fernandez, Hasay, etc. The only ones who can really compare or exceed her relative abilities are Ryun, Lindgren, and Slaney. Having her run dual meets week in and week out against (in most cases) vastly inferior competition is NOT going to help her in any way.
Since she won an indoor US title, took silver at the outdoor US championships, won the World Jr. 3000m, and made the World Championship finals, it's safe to say that "racing experience" from college is one of the last things she actually needs.