My same issue; the only place I have a little extra weight is my belly pouch. My husband and daughter both battle with their weight and have more issues with overall tummy than just a pouch. We all suffer from gluten intolerance and other food issues/allergies/intolerances. I have noticed that most of the people in my Celiac support group all have somewhat of a tummy pouch.
I've also suffered from Candida/yeast my entire life. I think having too much of that in one's body also contributes to stubborn areas not wanting to go away. Getting rid of Candida at the age of 12 is so much easier than trying to get rid of it at the age of 40. I had a yeast infection every month I had a period. Every month. And I wasn't a big sweet eater; for some reason, Candida just liked my body, I guess. Probably because I had food issues all my life but didn't know it until I was 40. Five years later, I'm still wrestling with getting my body healthy.
Not cause for alarm per se, but if she continues to grow taller and slim down but the tummy pouch never seems to go away, you might want to have her checked by a Naturopathic doctor for food issues. An allergy or intolerance might be blocking her bodies ability to regulate/tone up that area of the body.