Don't let it get you down, D! Numbers on the scale and numbers on the tag are just numbers--they do not define you and they don't have anything to do with your value! There is so much more to you than a number!
Besides, I wonder if the costume you ordered is Junior sized and not Misses. Junior sizes are designed for skinny teens with no curves. Even if I was at my lowest weight, I would not fit well into junior sizes because I have curves. Love your curves, D! (and from what I hear, guys love them too!)
Don't let this discourage you! Stay with us!