Bread is not a good form of diet for a pony. If the grass she is eating is lush and green, this is all she will need, unless of course you are exercising her very hard, then she may need some extra 'fuel' in the form of pony nuts that are enriched with vitamins and nutrients. Hay is also good.

 Ponies and horses like apples and carrots, but they also like grain and hay. They also lick and chew salt blocks.

 If you want to feed her snacks for good behavior then you can feed her thewse peppermint bars. They are small bars that horses get fed for good behavior. There is also horse and pony pellets for regular food something to help with there digestive system. That's all i know of hope this helps.