While googling Rachel Millner again, I found these HAES "experts":

Fall Ferguson, JD, MA, is the Program Chair of the Health Education Program at John F. Kennedy University in Pleasant Hill, California. She teaches courses on health policy, community health, health coaching, educational methods, and body acceptance, among other subjects. Fall served as the President of ASDAH from 2012 through 2015, and currently chairs ASDAH’s Public Policy Committee.
Oh, looks like Fall died last year...of a diabetic-related condition:

Deb Burgard, PhD, a psychologist specializing in eating disorders and sexuality, is one of the founders of the Health at Every Size® (HAES®) approach. Deeply interested in both stigma and body image, and how people find ways to cherish the bodies they were taught to distrust, she uses these lessons in her clinical work with people suffering from various forms of body estrangement. She has written and done research on these topics and co-chairs the HAES® SIG for the Academy for Eating Disorders, serves on ASDAH’s Public Policy Committee, and on NAAFA’s Advisory Board.

Dana Schuster, MS, is a Health & Fitness Instructor with a Masters in Rehabilitation Counseling. She co-taught the Kaiser Permanente Great Shape exercise class for thirteen years, co-founded Women of Substance Health Spa (open 1997-2001), and currently teaches exercise classes at Every Woman Health Club in Redwood City, California. Since 2005, Dana has been involved in School Wellness Policy development and implementation as an avid promoter of the Health At Every Size® model. She is the married mother of two adult (and fabulous) sons, has a terrific daughter-in-law, and prefers to describe herself as a “Freelance Agitator & Advocate for Integrity.” She is currently the Vice President of ASDAH, chairing the Internal Policy Committee and serving on the membership and blog committees.
-So, somehow this awful Millner woman telling a young, healthy, vibrant student athlete to pork up makes more sense now.

The worst part is that loving, trusting parents who just want to get help for their kids will take bad professional advice to heart instead of trusting themselves and their own common sense and intuition.