Ah, this was great. Throughout it, I was wondering what she was doing and then, "Just wants to be thin," and I [i]knew[/i]. I relate to this personally and it's beautiful. I like the short stanzas and lines. It's just impact after impact of emotion without boring the reader.
My only critique would be the last two lines sound awkward in my head and when I read them out loud. They almost. Don't fit? I don't know. They're just awkward lol.