Have her wear a black shirt (a band tee shirt from Hot Topic might be good), black pants, a black wig, black lip stick, and a lot of dark make up. There is really not a "costume" it is just a matter of compiling a bunch of black accessories and make up.
Buy fake piercings and put them in your brows, lip, nose ect. And wear some really big black boots.
A goth prom queen a corpse prom girl A kitten a black eyed P a 50's teengirl
The best costume for a girl is a witch costume because you just need a black cloth, monster make-up, some blower of the hair! and wallah! DONE!
You make a costume and paint your face
Yes, my sister dressed up as a cowgirl/ saloon girl for Halloween last year and went to a party in it. It makes a fun and easy to make yourself costume.
You don't you buy them
Use your imagination.
Go to your local costume outfit store. But they are only open around Halloween season. You can order this costume any time of the year on line. Or you can always make your own.
It's simple... ...we kill the Batman.
One can find an executioner costume for Halloween online at websites such as Amazon or eBay. One can also make their own executioner costume by following tutorials online at YouTube.
There are a couple links below that detail how to make a Kevin Jonas costume.
you go buy a giraffe and then you put the giraffe on a dog and theres your halloween giraffe costume
You can buy one or rent one from a costume store. If you are feeling really creative, you can make one yourself.