I am pleased to hear you aren't planning to embark on any weird starvation style diet Molly.
You have raised more than a few points here ; I'll try to answer as best I can.
1. Do Vitamins and supplements contain calories - Everything has a certain calorific value, but vitamins are so calorie poor that they can be practically discounted as a source of calories. With respect to supplements, their calorific value depends on what type of supplement you are talking about - There are dietary supplements for bodybuilders and suchlike, and they may have quite a high calorific value, for example - but those supplements designed to offer vitamin or trace element support are likely calorie poor.
2. Just because the model or the press article says that the person in question is not malnourished does not mean or guarantee that they aren't. A personal statement or gossip based opinion does not constitute evidence.
3.Again, in general terms, the calorific cost of digesting, breakdown and transport of food is practically negligable with respect to the calorific content of most food groups and can be discounted, with certain specific exceptions, such as celery, or drinking a cold low calorie drink.
4. Dont take the 1,000 calories as gospel, Molly - That was meant as an illustration only of an absolute daily minimum. The exact amount varies depending on which study you look at, and will also be dependant upon whether you are male or female, child, adolescent or adult, pregnant or not, etc. A number of studies recommend 2,700 calories a day for a healthy adult active male, and 2,000 calories a day for a healthy adult active female.