I've been working with this one mare for a couple of months now and we've come a long way. She's still fairly young and a little bit green, but she's got potential. The main issue right now is that she's pretty stiff. She has no problem in a large ring, but she's a big horse (16hh, part draft) and the way she maneuvers herself in a small ring is often awkward and stiff. She tries to cut her corners, collapses on the inside bend and drifts inward. She often throws her head to the inside as well, even along the long wall, and when I try to straighten her head she resists.
In attempt to fix this, I usually move my inside leg back slightly and apply pressure (she responds better to that than just pressure), pulse the outside rein to balance her, and use the inside rein to create bend. I twist my shoulders towards where I want to go and keep my hips aligned with hers. Still, while it works in a big arena, in the small one she's drifting all over the place and I can't seem to get her into her corners while keeping the appropriate suppleness and bend. Is there anything I'm doing wrong/should change, and what are some good exercises to keep this from happening?
Any help would be greatly appreciated.