My friends child is overweight and shes oblivious

My friends daughter is 10 and weighs 160 lbs. Her ankles and knees always hurt, she gets winded walking and she has high blood pressure. When she comes over I have to put food away because she will finish an entire large bag of chips and will raid the pantry and eat whatever she can find. I feel like such an asshole for hiding food but I don’t know what else to do. She eats mostly pasta with butter, grilled cheese sandwiches and chicken strips at home. Her mom says she’s just grown a lot and is going to be tall like her dad. She doesn’t offer her healthier choices and disregards what the doctor tells her. I have recently seen her weight gain really accelerate and it’s breaking my heart. Would you, in a loving way, express your concerns to the mom? I feel compelled to say something, but how on earth can I do that without sounding like a jerk 😭 There is more than just poor diet causing this and I love that little girl so much. I just want her to get to a healthier size so she can do normal kid stuff and be healthy. What are your thoughts?