I have no advice really, or experience, but couldnt let this sit at zero replies. I know how hard it is when you put yourself out there, and watch the post move to the bottom of the page with nothing.
there seems to be alot of PCOS sufferes that i know of, in my family, and my brothers both married girls with it. One is finding weight watchers very useful right now, as she feels its a break from all the hard diets, and restrictive lifestyles alot of them promote, like TF, and KM.
I guess you have googled PCOS diets as well, and all, so really the best thing is to keep following these programs to at least maintain the weight. I have learnt tho myself from many years of strict dieting, that its when I dont diet, and just lead a sensible eating plan (weightwatchers) and exercise, i get results. my metabolism dropped really low when I restricted myself. now I eat alot of food and it has helped me loose weight, as I burn it all of no problem. I know you said you tired all those 5 meals a day, and all, without success
but please dont loose faith in there being an answer. keep persevering, and there will be a solution I am sure.
goodluck to you and your daughter, and I hope she can loose some weight soon.