Negative.It's a built-in thing to stop people from sharing files across a local network. I hope you noticed that when you turned on sharing in iTunes that it said "For Personal Use Only" meaning just that.
If you want to connect to your sister's machine, get her IP address in the network and make sure her music directory is shared. The type smb://192.168.1.100 or whatever in the Finder menu option marked Go... and mount the drive. Then you can copy everything to your local machine.