I would get a grazing muzzle on the pony if she is on any amount of pasture. Ponies are notorious for being easy keepers, and the majority of pony breeds are bred to work hard with minimal feed and keep weight. Dry lot is a viable option, if you are willing to go that route, but I think a healthy amount of grazing, (restricted by a grazing muzzle,) could do her some justice. I would just work with her 3-4 times a week, or more if you have the time. Get her ground manners impeccable, then work from there. Look into natural horsemanship, you will find some really neat things to do and have fun with. I would mix it up between jogs and lunging sessions, maybe stir in a bit of jumping once she is warmed up. Just be creative, and explore every avenue of desensitization. If you do it avidly, you will mix in work and the both of you will be having too much fun to notice. Driving is also a avenue you may want to visit. But other than a solid exercise routine, keep her on limited grazing, low-quality forage, (by this I mean no alfalfa or leafy hay, not moldy cheap crap,) and no grain. Right now, all of my easy-keeper horses are eating swamp grass and keeping weight beautifully. It is the perfect diet for horses that get minimal exercise. Keep an eye on her weight, and if necessary, mix in some higher-quality hay until you reach a good balance. Good luck with her, and have fun!