I would ride her to a long, straight dirt road, fence line or big field. Ask for a lope and circle if you need to slow her down, but keep her in a lope, never pulling both reins. And lope, lope, and lope some more. When she's tired, keep loping. When you feel like it, and she really wants to slow down, then ask her to slow down. Repeat the next day, and for as many days as necessary. It wont take long before she realizes a nice slow lope is much more energy efficient than jumping all over the place like a rubber ball.