I love the movie! And I think the point of the whole "I like you, just as you are" idea is that she really was okay as is. In the book which is written in diary form, she does bounce around in weight more, but it's all at the level I think all of us would maim kittens to be at.
And while today I find it challenging to understand the struggle of someone who is tortured over 20 pounds or less, I CAN remember (back in my teenage years) when I thought I was fat and, looking back, I wasn't. I had probably 20 pounds or less to lose then, now that I think about it. While our road is longer and complicated by factors those with only a handful of pounds can never understand, they share common traits with us: a need to get a handle on what they eat and a dissatisfaction with how they look. I think those are things we can certainly identify with even if we envy them!
Oh and one thing I keep telling myself: Maintenance will be just as long for someone who lost 20 pounds as one who lost 100+. But think about what we'll know we're capable of!