Good question! I'll ask her, but from previous conversations, she sticks to American ingredients.
My understanding is that she tries to do most of her testing in America because between France and the US, there is so much variation in the raw ingredients. The flour, the butter, eggs. So different. It's just easier to test in the US. I know she brings American ingredients (flour, etc) with her to France, but it's mostly for personal use, not testing.