If she has a favorite picture of the two of you, buy a really nice frame, insert the photo, put the frame back in its box, and wrap a ribbon around the box.
That same picture can be printed onto a really fun mousepad.
If she likes wine, you can buy a good bottle for a very reasonable price. Take her someplace special—a park, your front porch, a riverbank—and share the wine.
Is there anything local that she’s always wanted to visit but never does? We all have places that we walk or drive by—museums, historic buildings, interesting stores, natural attractions—and say, “I’d really like to go there sometime.” You could spend a morning or afternoon making one of those things happen.