And explain to me once more why McDonalds should pay for her mistake?

I suppose I'll have to watch it to see how poorguy got convinced it wasn't her fault. Documentary film makers can be just as effective as Madison avenue at tweaking ones perceptions.

If I buy a knife then on the way home I trip and fall on it, can I sue the knife maker for making his darn knives so sharp?

One expects a knife to poke and cut. One does not expect ones food to put one in an ER.