I'm trying to send my girlfriend some traps to help her get started; can't figure out how.

Also, apparently traps aren't tradable? Wtf?

Yep, traps are not trade-able, except for the diamond bought master trap.

But the next time you would like to send something that IS trade-able, there is an envelope looking button near the bottom of your inventory. Click the item you want to send, and then click that button. A pop up will... pop up and you can type in the name of the person or select them from a drop-down menu.

You could alternately send her some gold if you have her send you a worthless item and put a COD fee on it. Then she can buy her own traps.

(The traps are not trade-able to keep people from doing things like "omg I found the most awesome pet, send me a trap." I think the idea is, you always need to be prepared)