That's awesome! My husband's favorite thing I ever did was a treasure hunt on one of our first Valentine's day's. I bought a box of those little valentine's card that we use to give each other in elementary school and wrote hints on the cards leading to the next card/hint. At the end there was a giant candy bar or something. I probably made the clues rhyme knowing me. "Roses are red, violets are blue, you might find something in a shoe." He said it was the neatest thing anyone had ever done for him. 🙂
You could just send her from place to place around the house or hand out cards to family/friends so she has to hunt around various locations. I also did a similar thing one year, but each clue was a puzzle. I went to a craft store that could cut a piece of card stock paper into puzzle pieces. Assemble the puzzle for the clue to the next location/person who had another puzzle. Enjoy your trip!