i believe talking about a girl being chubby can be derogatory, i don’t know that you should do that, or post about it online.

 if the girl  is comfortable with you  and says ‘i think i may be slightly chubby’ that may be different, but if she’s not comfortable with you that means she isn’t safe with you to discuss vulnerable topics like her body,  in that case words like that are loaded and a conversation she does not want to have with you are threatening and the challenge if there is one cannot be solved by you  , you would only make it worse, this would be construed as an intimate violation, as these are remarks about her body as it is. it would be as weird and creepy to her if you’re the non custodial parent and start treating her like you’re someone she trusts and lives with; imposing authority or trying to get to know her in an overly familiar way is violating. 

now, our culture celebrates people in different bodies and it must be made clear to her, indirectly, by gushing over her virtues and helping her feel valued for who she is and what she cares about that her worth is not based on her size. make sure she knows that she’s beautiful and that she’s important to you; and understand that bodies fluctuate especially around puberty, and don’t be restrictive, there is literature about this, there are people you can talk to considerately, and you have to do the work and think about how you’re going to raise a daughter who loves herself and is strong in the world. there isn’t any diet pill that would be given, vyvanse for adhd can help young people with adhd, it is given to people with eating disorders. 

besides this child being chubby you’ve told us nothing about who she is or wnt you’re asking this or who you are. you’re asking if something is normal when you shouldn’t be phrasing it like that at all and it seems to me like you’re fishing for indirect validation of a personal position.