In my opinion (and maybe somebody above said it), the right way is the way that works for you. I had weight loss surgery 4 years ago, and that didn't work. This works for me. I totally agree with/bought in to the IP way of losing weight. I have tried every other diet and none of them worked like this plan.
Also, maybe she knows 2 people that gained their weight back (all the people she knows). That isn't a good measure. I think it was a sales ploy. Also, for years and years and years, the balanced diet approach has been the mantra for all doctors, etc. But the trend is changing. We have received some daily videos from IP discussing this recently.
As far as the impact on the diet that training for a 10K will do - talk to your coach. I am sure that they will up your packets per day, which they should. From what I remember at the first meeting, an 800-900 calorie/day diet is not sufficient if you are training for such an event.
Good luck. Don't listen to the nay-sayers. Do what works for you.
Fun in the Sun Summer Challenge
5.8 lost, 19.2 to go