Once she has mastered the sidepass, it isn’t necessary to keep doing it – now she is ready for the challenge of the half pass. Also do other dressage things with her, such as shoulder in, then haunches (in and out, for which there are words the spelling of which escapes me just now) and other things that make her think. Do spirals, serpentines, figure 8s, small circles around assorted things or in various places. Cavaletti are also good, if you can rig them up, and a square of poles on the ground over which she must cross in various directions. Even if dressage is not your ultimate goal, it is the best foundation for every discipline and it makes her think and concentrate on what she is being asked to do, rather than looking around for some dragons lurking in the bushes. If both of you are focusing on what you are trying to do, she will have less opportunity to find something that amuses her (such as leaving you on the ground). If you are cantering, do a lot of lead changes as well as changes of direction (I’m not there yet with mine). Set up a “trail” course with a piece of carpet on which she must stand, or a wooden bridge, a mailbox from which you remove something and put it back while she stands – nothing you might ever do on a real trail, but more interesting things than just plain riding. If there are endurance rides in your area, consider getting her fit for them – with her breeding she should be good at that. Another thing I sometimes resort to is riding (in a ring or some other fenced area) bareback and just meandering around for a short time to confuse them. When they think they know what you are gong to do, they get bored and throw in something that interests them, regardless of how you feel about it.
It is never the horse's fault