It's too early in both her career and her development to know. At this stage, such a statement is nothing more than conjecture.
Being relatively short, if she fills out to a significant degree, then yes, it will cause problems. But there are three important factors to keep in mind here.
First, not every slim female high school distance runner has an eating problem. Many of them are just built that way, with an obvious assist from the number of calories they burn off daily. This by itself doesn't mean they have an eating disorder.
Second, not every thin teenage girl adds major weight when they develop into a young woman. Of course, they don't look the same at 20 as they do at 15, or the same at 25 as they do at 20. But while there's no guarantee she will stay slim, there's also no guarantee she will dramatically add to her hips and/or chest. Or, looking at it another way, there's also no guarantee she needs to develop an eating disorder to stay slim.
But, in many ways, this is the most important factor:
Third, it will depend on the kind of coaching she gets at the next level. If she is properly guided through a gradual transition to college training and college expectations, with a high degree of sensitivity to how she is responding, then she should do extremely well. If, on the other hand, she is thrown into an all-too-common collegiate meat-grinder system, then the result will not be pretty. The vast majority of 18-year-old girls are simply not going to survive, let alone thrive, in a system in which they are relatively quickly thrown into high mileage and high intensity. This applies to those with high levels of talent just as much as it does to those with moderate levels. The Darwinian only-the-strong-survive approach is not a substitute for enlightened and educated coaching.