Oh, a conundrum! I know etiquette says I shouldn't say anything, but....she's only 12 and she's going to have this problem all of her life if no one takes care of her. And frankly, it's nicer to feel normal for a while than to spend your whole life worrying about what you put in your mouth. It's also nicer when people love you even when you are fat instead of trying to bribe you with clothes you don't fit into and vague visions of what life could be like if you were thin.
Edited to add that I've talked to boyfriend about it and he doesn't think anything is ever going to change. But i just hate that hint of hopelessness!
Smarterthanu's boyfriend is worried about his sister's health, and I'm sure that being that size is no picnic for her (the sister) either. I very much doubt that she feels "normal" being a size 22 or 24 at her age and height, not being able to enjoy simple things like going swimming with her friends, or shopping for cute clothes, or getting dressed up for formal dances, without feeling self-conscious every single minute she's doing these things, IF she even still does them. I know first-hand that I never really felt "normal" when I was obese, even when I was surrounded by people who accepted me and didn't constantly tell me "Freaky, you're too fat," etc. I knew it for myself, from looking in the mirror, and feeling constantly clunky and lethargic, everywhere I went. Sure, it took a lot of effort to get myself down to within shouting distance of normal, and stay there, but I still remember how good it felt the first time I was able to buy normal-sized-person clothes, and put on a bathing suit without feeling like a fat blob, and run up the stairs without getting winded, and look in the mirror and actually feel like I looked nice. I wasn't that gung-ho about losing the weight when I started, because I didn't think I could ever do it, but in retrospect, it was *definitely* worth it. I don't "spend my life worrying about what goes into my mouth" now either, I actually prefer healthy food to junk (for example, I don't like French fries or onion rings anymore, so if I'm eating out, I'll pick salad over that), and while I still have a bit of a weakness for chocolate and other sweet things (but mostly chocolate), I make sure to enjoy those things in moderation, and balance them with healthy food. But Bethalize, you're right, those people were definitely being rude buttinskys to accuse you of "unhealthy habits" when they didn't know that there was an underlying medical condition that you had no control over.
If Smarter is willing to build a relationship
with BF's sister, and be a good influence in her life, then that would be a wonderful thing that could get her going on the right track, not just health-wise, but in every other way. Every girl should have positive older female influences in her life, there doesn't seem to be an older sister in the house, and it sounds like her mother is kind of falling down on the job. I was a firstborn myself, so there were a lot of things I either had to figure out on my own, ask my friends to teach me (like how to put on make-up, for example), or just make do without knowing. But, if Smarter steps up to the plate and is willing to be that person for this girl, then I think she'd have a much better self-esteem and quality of life. Even if she doesn't actually lose that much weight from Smarter's influence, she'll at least feel better knowing that she's "important" enough for her brother's "cool" friends to take an interest in.
Oh, and another idea......maybe to make this less teachy-preachy, Smarter could ask her boyfriend's sister to tell her/teach her about something *she's* into, like, if BF's sis likes art, then Smarter could maybe get her to give her some pointers on drawing or whatever, or they could take an art class or tour an art gallery together. Like I said, it's not just about trying to get the girl to lose weight, it's about providing her with a positive role model that she doesn't have at home. I'd be saying the same thing if Smarter's boyfriend came from a family of alcoholics, and he was worried that his sister was heading the same way. In fact, some people say that overeating is a harder addiction to conquer, because, while a person can swear off alcohol, drugs, or cigarettes forever, it's impossible to stop eating completely.