I've also bumped up the amount of time at the trot I ask her for while longeing or roundpenning, making her stick it out for at least three and working up to five minutes at a time. It's interesting for me to watch for her rebellious moments which almost always pop up when we're doing groundwork, mostly right when she starts to get a little tired or when I'm asking her to challenge herself mentally. She does some serious teenager head tosses and speeds up and in the roundpen sometimes even gives a little kick or buck, but as long as I wait it out and ask her to change directions a few times she calms right down.
Also, giving her those massages with long heavy strokes along her spine that the vet recommended is definitely having a beneficial effect! Where she used to move away from the saddleblanket when I would go to put it on her she now stands still and doesn't try to avoid it, and she also moves around a lot less when I cinch her up. I think it improves our relationship too and am taking advantage of her being relaxed after her massage to really get her sacked out in the areas where she's always been a little more sensitive - udders, mouth and nose.
I have another lesson this afternoon, we'll see how it goes!