I don't think I've ever seen any of Nigella's shows featuring vegetarian and vegan recipes. I'm sure Nigella could provide lots of tasty, inspirational recipes, maybe an idea for your next book?
Nigella has included many vegetarian and vegan recipes in her previous cookbooks, though none of them are exclusively on this theme. However in her new book, AT MY TABLE Nigella has included an at-a-glance guide in the index to show which recipes are vegetarian and vegan. So it is very quick and easy to identify these recipes.
On Nigella's website she has also collated a selection of vegan recipe suggestions and vegetarian recipe suggestions to provide inspiration. You can also search the recipes on Nigella.com by clicking on the "More Search Options" tab that appears below the "Find A Recipe" box, when you use this box to search for a recipe on the website. The search options allow you to filter the search to show vegan or vegetarian recipes and there are other filters such as gluten-free, dairy-free and egg-free.