I guessed what this post might be about from the title. I am sorry you're hurting and what's happened to your daughter. It must be terrifying and feel so out of control.
I am a sufferer of bulimia and have had partners with drug addictions. I would liken my experience of ED to addiction, in the sense that it is all-consuming, the habit itself is somehow fulfilling, the world shrinks to the pattern of binge/purge, the number on the scale or on the clothes label, in the same way that an addict's world shrinks to the dealer's car and their paraphernalia.
I know not everyone subscribes to the 12 step model of addiction, but I believe some of it holds truth, especially the part that says "you didn't cause it, you cannot cure it and cannot control it". I think this is true of ED. ED seems to build codependency like drug addiction.
I never let anyone else into my ED or told them (it just didn't happen that way for me), but I have known anorexics. There is always a circus around them, understandably, to try to save their lives. Parents and boyfriends cutting labels out of clothes or otherwise trying to cotton-wool the ill person so that they won't get any worse, the same way that the wife of an alcoholic might tip drink down the sink.
I think I might understand your motivation here, to want to do something. But I feel you might be blaming H&M because you want to strike out at something, because the illness is hidden inside your beloved daughter and you can't lash out at her to get to it.
Maybe some family therapy would be of help if you are able to access such a thing privately.