Stephanie - what size shoe do you wear? Are your feet still growing? While you don't want your boots to be too roomy I feel roomy is better than too short in the footbed.
If the footbed is too short in open toe bindings your feet can slip forward. If you have closed toe bindings you will be stubbing your toes on the front of your boot every time you have a hard landing.
How does the rest of the binding feel? Does it support your ankle well, provide adequate support and lace/strap down snugly? If the rest of the binding fits I think you probably have the right size.