Another thing to add to this, as an autistic person:

think of your daughter's palette as a tree.

Whatever she normally eats is the base of the tree.

Build on that by adding branches to the tree. For example, if she normally eats cereal for breakfast, sandwiches for lunch, and pasta for dinner, you can change the varieties of each of those things.

Try to keep the same routine as much as possible by making sure she eats roughly the same things at the same time.