The only choices for return postage:
-IRCs
-Exchange British pounds for Australian money and send it to her (make sure you know how much postage costs in Australia).
-No return postage at all.

If you want to get something back, I suggest you either take the first or second advice. But the first advice will be the #1 choice.

Yeah, as -Lil1- stated, your only options are IRC or Australian postage... although out of your options the only valid one is cash... neither american stamps nor british stamps would help at all- seeing as how they wouldn't be valid for sending something outside of the US or England respectively.
-Matt

Thanks For Help - But I Don't Really Want To End Up Doing That!

you can put IRC's or australian stamps!

I am writing top rihanna VV in Australia ( I Live In England ) what stamps can i put for return? British ones, american or just send some money?

Thanks,
Sam