I know of several quilting books for children, but none have swatches. I tried a google search, but just found my old favorite quilt books, not what she wants with the swatch.
It might help her to do a google or Amazon search, since she knows what she is looking for. Maybe the swatches came with a special promotional book, but the actual book doesn't come with them. It could be that looking at the books would trigger a memory that could help her find it.
Good luck in the journey to find this book.