You said she needs to be able to access "those files" did you mean on all the systems on the LAN?
Sounds like and FTP server(with proper port forwarding
see http://http://www.portforward.com/) would suit you in this situation. Set it up as one of her "Network Places" on the travelling system and she can access it like any other drive mapping (drag and drop only/no drive letter)
Never really tried VPN. The network guys at our home office configure our Cisco's at the data center.
VNC (web) doesn't allow for file transfer. Can't help you with the LAN VNC client...can't get mine to work (yet) over the net either. (my LAN yes, the net, NO, webclient yes/easy/no file transfer)
If you know the port to forward for RDP, that would be another way to go, but then again, no file transfer.