Wasn't quite sure where to put this ques

Wasn't quite sure where to put this question, but this seems as good a place as anywhere else. I have an almost 11 year old daughter who is quite large for her age and height. I adopted her so I do not know what her biological parents looked like. She is quite the eater and has gained quite a bit of weight lately. I would venture to say she is always thinking of her next meal. I adopted her when she was 7, and I believe she had poor nutrition prior to living with me. I doubt she even got 3 meals a day. Trying to keep all this in mind, I need advice on how to deal with this. It can be quite triggering for me to sit with her at dinner as she displays eating habits that I hated about myself when I was an overweight child. Honestly, sometimes I can't eat when she is eating. I try to fix nutritous meals, and I pack her lunches. I don't know where the weight gain is coming from. I think she sneaks snacks and eats extra when she is not with me. I do not starve her. I have tried to speak to her about "eating healthy". I have never called her fat. Due to the fact that the healthy eating strategy wasn't working (i have tried so hard), I recently have been a little more open with her regarding my concern over her eating habits and that we need to "work together" to eat right. She asked me if I think she is fat. I always tell her no, but recently I feel she needs a reality check and have used the words "i don't think you are fat, but I am concerned over how much weight you are putting on" (25 lbs in one year). I don't know how to get this in check before she hits middle school and all the cruelty starts with the "mean girls". she is very popular now, happy, enjoys life. I don't want to plant a seed in her, and my worst fear is that I am going about this all wrong and she will develop any type of disordered eating. Like I said, I need help with how to deal with this. I know my eating disordered mind clouds my ability to help her. sometimes I feel too critical, sometimes I feel I am neglecting her because I am not firm enough with her diet. We did recently join a gym, so I am hoping to get her moving more (she hates to excercise) and I have her in taekwando. I have thought about taking her to a nutritionist, but wonder if she is too young? I don't know what to do. I just want her to be healthy and to be able to have energy and keep up with her friends. I don't want her to suddenly feel self conscious because she can no longer wear children's cloths and we are shopping in the adult clothing section where the trendy clothes for kids don't exist. Perhaps I am just a crazy, obsessed mom...but I have had family and friends (and her medical doctor) express concern over these same issues. Any advice would be great. Thanks, Tracy