Today, from the moment I got on, she was almost 100% consistently soft at the walk and trot - I think she's made the mental switch over from bracing to softness. I think she's convinced that being soft is more comfortable and the way to go, and the session where she reverted to bracing may have been the turning point. She got to reevaluate her old way of going and see for sure that it wasn't as comfortable as softness. There are still moments of braciness, and there will continue to be, especially as we try out new or more strenuous things - horses will sometimes revert to older, known behaviors in these circumstances. One area in particular we need to work on is the first step of backing and the first step of walk after halt - when she's halting, she tends to lose focus and braces until I regain her attention - I think this means that I'm losing my concentration when she's halted and therefore I'm not continuing to give her direction, and then we have to recover that continuing focus and connection from the halt into the first step of backing or walking.
Now that the basic softness is there, we can begin to refine things. We did a lot of transitions and figures, with the trot as our main gait. We did some shortening of stride at the trot. We're starting to work on lengthening of stride at the trot - this is somewhat of a challenge for her as it can result in faster steps not longer or some braced steps. So we did a lot of transitions between shorter and longer strides at the trot, and if she thought about rushing or bracing, I directed her into figures to allow her to rebalance and refocus. Now that she's no longer doing the "curl-up" instead of softening, I'm encouraging her to adopt a somewhat lower head position, where the poll is not the highest point, and to step up into this from behind. This will help a lot with the lengthening of stride, and with maintaining softness throughout her neck and shoulders.
We did a number of sets, and then for our final test of the day, we did a figure eight with some modest stride lengthening on the diagonals and shortening on the turns, went straight and halted while maintaining the softness - she absolutely nailed it! And we were done for the day, and she got a well-deserved rinse off. I just love this horse - she's amazing to work with!