This site has a PDF you can download that had different patters you can work on in an arena setting: 10 Fun Arena Exercises
Click on the link next to the orange arrow at the top of the page that says "Horse and Rider's 10 Arena Exercises".
Other things you can do is set up optstacle courses and make up patterns to go around them. You can do this leading her and riding her: Obstacle Course Work
Other than stuff like this, I'd say get out on the trail as often as possible. Let her know there is other stuff out there to do besides running a pattern as fast as she can.