backstory: I married my husband almost 4 years ago. we have been together 8 years. he has a brother (my BIL we will call W) who got married and had a daughter. him and that wife divorced (we will call her J). And he has a new wife. we will call her K. anyways my niece is 6. i have been there since she was born. kept her a lot when she was little. I don't like my brother in laws newest wife K. She lies, she is a manipulator, causes drama. I just don't associate with her. I feel it is for the best. my husband and i have loved out of state for the last 4 years and now we are back and we see our niece a lot. So current story: my niece is ADHD. She is on medication for it. (My husband is ADHD and he takes meds too) the medicine makes her so hungry. She eats constantly. which is fine. She is also skinny/petite for her age. And the meds boost her metabolism. well my SIL, K, (my nieces step mom). won't let her eat as much as she wants. *disclaimer: I would understand if my niece wanted to sit and eat junk food and K said no. that would be ubderstandable* but my niece wants more pot roast. or more BBQ. *She is here with me today, and from 7 am ate: pop tarts, toast, pack of crackers, bowl of BBQ, 2 glasses of chocolate milk, then wanted pot roast. all before 10am.* anyways a few days ago she wouldnt let my niece have more foodI asked K why she can't have more food when the kiddo was crying that she wanted more FOOD and K' s response was "it will give her a tummy ache". Alright that makes sense.. but she isn't complaining of a stomach ache.. now back to me keeping my niece today. my daughter was trying to squeeze into this littke area to hide from my niece (playing hide and seek, my daughter is a lot younger and of course smaller). So my niece tries to get into the same spot and I said "no babe, you are to tall". She respons with "no I'm to fat". And I said "no you're not. you are tiny. why do you think you are fat". And she says "K has been telling me I'm getting fat". guys I could see K saying this and to be honest I just want to punch her. you don't tell a 6 year old who weighs 40 or so pounds that she is fat and not let her eat! Especially when the medication makes her hungry!! I don't know how to proceed because I feel like K will deny it, and my BIL W thinks we are the bad guys beause he doesn't see that his wife lies all the time. (I tried to point it out).. I seriousky want to annonomously tell my nieces mom J. because if it were my child, I would want to know. but I know J has been trying to get full custdy and while I don't care much for K... up until now I didn't see a reason to keep K and W from their child when I thought they were perfectly good parents. but I don't have physical proof to tell J. what should I do? edit #1: the medicine makes her metabolism speed up which causes her to be hungry. it's not just her constantly eating. the medicine is making it happen. And to be clear she is not over weight at all. She is in the 33rd percentile for weight.