Ideally evrything from the library on her computer should be transferred.
However if this is not possible then
If she bought her content form iTunes then the music will still be unplayable until you authorise your computer with her Apple ID. If it was ripped from CDs you should be good
Transfer the music as the link above explains. Then sync it properley with your latop it will as if you want to erase and sync. Say yes and then you can resync the content back to your ipod and it will now only sync with your machine