There are also heaps of books out there on emotional eating, which this could well be, especially if as you say she has some emotional issues. Basically it's where you eat to get a brief good feeling and bury the bad feelings. Of course this might not be the problem, but a lot of negative behaviours surrounding food are caused by a lack of the skills to deal with emotions/life events etc. From stuff I've read over the years I'd say don’t' focus on the eating, or the nutrition or exercise; its most likely a symptom not the problem itself, you need to find the underlying issue/s and help her to resolve/deal with/get help to deal with (depending on how severe they are) these issues.
Try to help her deal with the emotional issues, talk to her, ask her how she is, if she gives you any openings about stuff that's wrong/upsetting her then encourage her to talk - gently, don’t' insist if she clams up, leave it and come back to it at another time. Take every opportunity you can to show her she is valued and loved and worthy of love and care from those around her and herself. Keep trying to reach her, you'll probably get knocked back a lot, but show her she's valued and loved and that you care about her. If you keep trying to reach her that should show her she matters to you, that you care.
Of course I'm not a professional, personally if this was my situation I'd find a book on it by a trained psychologist and see how they suggest approaching it or even call one of the counselling hotlines and get some advice on how to help her or if you've got the money you could go see a counsellor yourself and talk to them about the situation and see what they say you can do to help. Keep in mind that if this is the problem unless she's open to help you won't be able to reach her, but keep reaching out to her. If she's having emotional difficulties I'd think you couldn't show her too much love and care.
This government site has some info on what they called disordered eating. It's aimed at the person with disordered eating, but maybe it'll give you some ideas if this is the problem and how you can help her. http://www.cci.health.wa.gov.au/resources/consumers.cfm
This post has been edited by Bubble11: 23/01/2013, 12:53 AM