Ideas for ハロウィン costume for 13 yr old girl?

probably been asked ONE MILLION times but im stuck and ive got a party to go to and i CANT THINK OF ANYTHING TO WEAR!!!!!!!!!!!!

me:
13 yrs old, moderately tall, skinny, red hair that is about 5 cm below the shoulder. OH YEAH girl.

i want something that's quick, but creative, and not toooooo scary.... ANYONE???


i need something によって the weekend so i can go buy it for monday night (31st in australia, not sure about what 日 of the week ハロウィン is in other countries this year)


THANKS :D
CAITYPIE