This question is a bit confusing. Nigella Lawson likely does her own cooking from her own recipes but she may also have help preparing ingredients, etc., when she films one of her TV shows. And for all we know, she may have help cooking at home too. If this question is asking if Lawson creates all her own recipes, I’m not sure.
It appears to me that when Nigella includes a recipe from another chef in one of her books, she gives the other chef credit carefully explaining how and why she may have adapted the recipe for her tastes.