She actually looks quite fit and healthy. Beautiful, clear skin and very healthy hair. Eyes are bright and alert. Lots of energy.
Her height and weight are fine. While it's true this is no longer "average" in America <modsnip> I joined the military in 1985 at 5'8, 108 lbs and passed all health checks and physical tests with flying colors. Most of the other female recruits were around my size as well. We were all just fine. I'm now at 120 lbs, BMI 18.2, and I'm just fine. Gabby looks like she is doing just fine at 18.3.