First, you have to teach the one rein stop not just go to yanking your horses head around. Any horse should have lateral flexion so it's a good thing to work on. I would ride her in the bit that was suggested to you. Why would you buy a well trained horse and not take advantage of it. Many older horses that have been ridden in a curb bit for a while do not go well in a snaffle. Don't follow trends just do what's right for your horse.