You can set up the mac to host a public folder on your local network that windows machines can access (there's a special tab that enables windows access). Once you get that folder viewable from the PC, you can just dump the files on the mac from the PC.
Alternatively, you could use a USB drive, or you could burn them to CD and read them onto the mac, or you could put them on a firewire drive and hook the firewire drive up to the mac, or you could host them on internet storage space (like a personal website) and download them to the mac....
or you could email them to her. That would be fun.
I recommend the local network option. It's the most useful for future needs.