Wow, that sounds pretty clever of her! To have seen only once how the top comes off, and then to take it off herself, is darn quick-witted. You definitely should try other mind games with her...

One thing our Aussie Eli loves to do is play hide-and-seek. For a quick game when I'm too tired to run around the house or yard, I take a favorite small toy of his, sit on the floor near the sofa, and hide the toy (under the pillow or sofa,in my pocket, over the back of the couch....). He'll look, find, and give it back to me for 30 minutes or more! When you want to make it more challenging, put your pup in a sit-stay in one room and then run through the house, drop the toy somewhere, go back to her, and send her off to find it. Doing the same thing outside is even more challenging! I'm always amazed by how good Eli's memory is and how inventive he can be about finding places to look for the toy.