It depends on whose 13yo she is really
If she is a freind or family child than I would ask the parents but probably get vouchers, but deffo ask the parents for which shop she would like. Probably Claire's or new look
If she is your 13yo then I would ask her what she wants for main ideas and then get lots of other bits, hair and make up related, tights are a good one they seem to love tights lol. Does she have iPod, mobile phone? Laptop? Accessories for these are also good.