My horse has been driven for her entire life, and while I can ride her with no problem, she isn't actually broke to ride. I can hop on her either bareback or with a saddle and ride her around, but she doesn't respond to my leg whatsoever. How do I teach her that squeezing means go faster? I can get her to trot by kissing at her and using voice commands, but she won't stay in that gait for very long, even with my continually kissing at her and talking to her, and getting a canter out of her isn't even an option (although right now I'm really just trying to master the walk and trot, so it's not that big of a deal).
She's about 16, if that matters. Any advice would be greatly appreciated.