I'd first of all ask yourself what is she in a waterford full cheek for? Then move the needs onto a suitable bit for driving. I've always used a Liverpool bit on all my drivers both competition wise and for leisure. The Liverpool has the bonus of various settings to be able to tweek for the horse you are using. I've always found all my drivers to go well in a Liverpool and they come in various styles. Personally I've preferred the straight bar then nutcracker action for driving, but of course all dependant on the horses preference to!
I really would get some advice as to harness fitment, Safety with carriage driving is paramount, so much could go wrong even from just a piece of harness incorrectly fitted.