it is never to late to train horses to drive! I prefer the older ones, they are not as stubborn generally, better ground manners also. Have you trained a horse to drive before? If not I will go along with everyone else and say get someone who is experienced to help you out with teaching her to drive. It is a lot harder than breaking a horse to ride. Getting the harness on is just like getting a saddle or a blanket on for the first time, just desensitize the horse to it. Go slow and let them get use to it, there is a lot of leather lines to tangle a horse that is freaking out in. Good luck, PM me with any questions. I can give very detailed instructions on teaching a horse to drive, but still suggest having someone experienced to help you out if you have never done it before.
I like halflingers, such sweet ponies, most are willing to do anything!
You know how to make a miniature horse even smaller? Leave them in the dryer a little longer!
"Don't ever regret something that once made you smile"