Saddles & Hooves

First off, Cadence got her hind shoes off yesterday when she got her toes trimmed.  I put hind shoes on for the summer when her feet began to break up in the spring.  Ultimately I'd like to have her go barefoot, and am contemplating pulling her front shoes in another month.  We'll see... I really like the concepts of natural hoof care, I just worry that it won't work for Cadence.  Her comfort is my top priority here, and that brings me to my next point.
On Tuesday when I rode, Cadence was... interesting.  She wasn't interested in bending to the right at ALL in the trot; like throw her right shoulder in and swing her body all over when I asked for bend not interested.  I could get bend in the walk and canter, but he trot eluded us. I contemplated back soreness( which was a no) and saddle fit, or a non-pain related issue, like hse just didn't want to do the work.  Cadence is really willing though, and (from my experience) seems to enjoy what we do, so the lasto ne didn't really fit.  After talking with my coach, I learned that she'd ridden Cadence in her saddle, not in mine.  She agreed that saddle fit may be an issue, as Cadence has bulked up so much in recent months.  She's going to ride Cadence again today, and I'll ride her in my coach's saddle tomorrow.  Then Saturday, we'll reconvene and discuss what we've found.
There is one other possibility. On the second day of the clinic (which I WILL get around to writing about... I swear) I used a clammer (sp?) on Cadence.  I've been able to find out absolutely nothing about them through the interweb, other than a post that Pia's Mom wrote about it.  It works sort of like a double bridle, but without the two sets of reins.  Apparently (from what I've been told) they're good for horses who lay on the bit, as they bump into the clammer and come off it.  It also works a little like a copper roller, giving them something to play with/concentrate on.  My coach used it again on her when she rode her (while I was in NYC) and it was after that ride that she said Cadence was wonderful, so perhaps the clammer's working really well when its being used, but having negative repercussions when its not?    This seems unlikely, for several reasons, but is still worth noting. Reasons I'm doubtful:
1) I doubt she's being vengeful and laying on the bit when she doesn't ahve the clammer, as she doesn't really strike me as a vengeful character...
2) She's only been worked in it twice
3) That's a pretty major repercussion...