many ways you can do that.
are they on the same router? Just find out what her IP is, and use a simple FTP program to log into her machine and copy the files from her iTunes folder. If you're not on the same home network, take your machine and a legnth of cat5 and plug in, so you can do the same. You can even connect the two via eithernet directly. Finaly if you have it, just take something like a USB hard drive with you and copy the files that way.