When you send something abroad, you should always be ready to have to pay customs fees at the arrival. That's the rule everywhere. You send you packet free of taxes (you should be able to get back the VAT you paid in your country as you export it). But the taxes have to be paid in the arrival country. That's the law for import/export.
The only exception is the E.U. where you pay the VAT of the country where you buy and there no custom fees between E.U. countries.
Other point, give the money to your girlfriend and let her go and get it at the post office. Don't go there by yourself or you may get an increased fee (a Kano price!). It happen sometimes...
