A treasure hunt sounds like a
great idea. I was nuts about that sort of thing when I was little.
"Obstacle courses" can be fun too, especially for high-energy kids. Set one up, figure out a reasonable time to do it in (by trying it out yourself and then shaving off a couple seconds if you feel you're slower than her), then get a stopwatch and offer some little prize if she does it in the right amount of time. Make it a time that maybe she won't get on the first go, so maybe she'll have to do it 2 or 3 times. That way it's a fun challenge.
Decoupage is good, too! You can go to a craft store to get little raw wood trinkets (coasters, signs, little jewelry boxes, keychains, whatever), some modpodge, and a sponge brush. Then gather up some magazines, comics, or print out some pictures and she can make some nifty things. A comic store I like recently had a thing like that set up for adults. It's a craft that pleases everybody.
Blanket forts are good too. Get plenty of blankets and pillows together, and maybe figure out roughly how to do it, but don't set it up until she gets there. Helping build the fort is half the fun.