Which part of the US is she comming to? You have to add local sales tax to some prices (for example it is 8.50% in NYC). Also unfortunatelly the best deals are not in the shops but on the internet. If she is staying in some place you know ahead of time you can make an order and ship it there. On multiple items combined from the same merchant shipping is low and you can get a great deal...

What exactly are you looking for anyway?

Also on the way back as already specified: MAKE SURE EVERYTHING GOES INTO CHECK IN LAGGUGE.