If she is into healthy foods I would recommend a vegetable spiralizer. I just went on the specific carb diet and I LOVE my spiralizer- it allows me to feel like I'm having pasta without the guilt.
I agree with many of the suggestions already given.
I'll add one: a bread maker. I love having warm, homemade bread and it couldn't be easier with a bread machine. I make bread often enough that I know the recipe, so it takes about 3 minutes to dump in the ingredients, and then you just hit "start" and have fresh baked bread in 3 hours. Fresh, hot bread with none of the preservatives than many store-bought breads have. Cheaper too. Awesome. The machine is a little bulky, though, so not great for people with really limited kitchen storage space.
On the pizza stone, I have one and don't really get the love for them.
Pickle keeper. We had one growing up, and I'm about to buy several for myself because I forgot how fantastic they are until my recent pickle kick. Simple and inexpensive but a great tool to have. They're also good for carrot and celery sticks.