I tried to use senuti, which definitely doesn't work.
After some research I tried using Jailbreak and iPhoneInterface, which lets me see the iPhone's Music folder... but it doesn't appear that I can actually copy things off the iPhone.

Does anyone have any thoughts?

It will cost you 20 bucks, but you have to download ipod access which also supports iphone. It's a great program, I just got it yesterday, impoted everything off my iphone straight into my itunes library.

Where can I find such a tool for windows? My girlfriend is using windows?

Why not try this wonderful iPhone to music transfer?
Wonderful iPhone to music transfer can help you easily copy music to iPhone, and is specially desiged for the support of iPhone. It can not only copy iPod, iPhone, PC music to iPhone but can manage the iPhone without the help of iTunes.
Come on to have a try and you will like it!

For Mac users, you can try this iPhone Music Mac, which is abusolutly good device to be used as the transfer between iPhone and Mac, the iPhone to Mac supports all fuctions as iPhone to Computer transfer, iPhone rip, iPhone backup software and can fast transfer, rip, copy and manage your music, videos, photos, podcasts and TV Shows between iPhone and Mac even without iTunes. All formats compatible with iPhone/iPod are supported.

Come to have a try and you will like it!

you could use iFunBox to get your music / videos / pictures down to a computer

The best about this tool:
it's free and u don't even need a jailbroken phone

Downside:
it's a windows tool

cu,
David