I'm not sure but I don't think your daughter would be allowed to follow the WeightWatcher system. I think you should seek the guidance of your doctor about this.
I'm not sure if you still need the answer - but yes I have, and it's excellent. I have been on the WW scheme on and off over the years (I know that doesn't sound a good recommendation lol) but overall it's a very good system, you just need to stick at it.