Hmm.. South Africa? Well, maybe you can send her a fashionable hat (that is her type of style), she'd probably love that [: You can send it in a fed-ex small envelope, not too expensive & it's not big.
What's really pretty and nice (plus small) are bangles. If you can find some thin bangles, she'd love those. Copper or fake gold tones are nice. Good ones are expensive, but you can find reasonably nice ones for a cheap price, under $20 I bet.
http://images.asos.com/inv/O/1/13/277887/Multi/image1xl.jpg
http://tiffanyslife.com/Resources/bangles.jpeg
(Like those, but those ones are expensive ahah. You can definitely find something simpler and cheaper, they don't have to look complex. Simplicity is golden.)
Or even a pretty necklace, maybe with her birthstone in it.
Or you can buy her a belt, earrings, tank top if you know her size, or something like that. But clothing is hard to ship unless you do use a small fedex envelope, so I would look into getting her small, thin bangles. If you have a Forever 21 or a Wet Seal in your mall, try those places first.
Happy birthday to her!