I agree 100% with kevinshorses, leave her in the kimberwick unless you're having problems. My sister has a quarter horse who is a pig in a snaffle; gaps his mouth, chews at the bit, roots at it, just kind of hates it in general. She rides him in a mild curb with a low port and hinged shanks western, and a kimberwick Engish, and he goes like a gem. So much of horsemanship is being able to make life easy for the horse, and to decide what battles are worth picking. Reliable trailering is a battle worth picking... a snaffle bit for a horse that functions well in a kimberwick is not.