"My point is that fat people get told to go to weight watchers while Anorexics are referred to a mental health team"
Well, most anorexics look in the mirror and see a person much bigger than the rest of us see, so there is the body dysmorphia issue that puts it into the MH category. Add to that the fact that anorexia will kill the sufferer in a vile, vile way. They know this, are warned about it, yet continue the strive for this impossible perfection that they have set for themselves as a goal. It's delusion on a pretty big scale.
I don't think that over-eating can be classed as a MH issue as such although I do think that mental state comes into it. When I was overweight (for many years, btw) it was partly to do with the fact that I associated food with comfort (have posted reams on this before) and partly because I LOVE FOOD and have willpower problems. Still do. However, I don't think that oveweight people have this massive internal struggle that anorexics do. Fat people look in the mirror and see a fat person. Sometimes it triggers them to go and eat more (huge already, what's another cake?) sometimes it triggers a desire for change (like it did with me) Anorexics will never like what they see in the mirror whilst they are still in the clutches of it.
Anyway...
Your mum is shit.