I have a hot horse (hot even when he eats nothing but hay) who is ridden in a half moon port french link kimberwick. The curb action is basically nil compared to others, but he too can be over bitted quite easily and 99% of the time responds quite well to it. The Saddlery :: Quarter Moon Kimberwick Bit (by Smith-Worthington) - Canyon Creek Saddlery
Your horse sounds a lot like mine - a bit rowdy and fresh, but has good intentions towards her job. Can you throw in some extra work on the flat (dressage or something) to focus her mind a bit more? But I'd be inclined to keep working with the french link - it is so hard to bring a horse back to a snaffle type mouth once they have worn a stronger bit for too long...hope this helps!