If you're going to order online, the system will know based on your e-mail address if you have a regular Hiptix account or a Hiptix gold account. I think when i did it the code was the same, so you can't differentiate that way. Call audience services, maybe, and explain the situation? They're pretty helpful. Your sister may have to place the order online, or give you her login information so you can order them using her e-mail address.
A work of art is an invitation to love.