> It is as if the iTunes website thinks the iPod is new and doesn't associate it with all that she has bought before .
>
No, it's the iTunes on her laptop that is new and until she associates it with her account details, iPod etc then
it does not know who she is. Ask her to make sure it is the most up to date version of iTunes then log in. Do this without having the iPod plugged in and it won't keep asking to sync.
Pre purchased music will also be in her library (on her previous PC) and she can transfer to the laptop alongside everything else. As soon as she has checked all her previously loaded music is 'saved' somewhere then she should go ahead and link her iPod to her the version of iTunes on her laptop. It will wipe everything but it'll be a simple process to just reload it (and it's a good opportunity to clean up as you go!:
To save your library go to:
File,
Library then
back up She'll need to do this on her previous PC
To import:
File,
add folder to library, then
browse to import by root folder of by album/artist. She'll do this on her laptop
If you have a wireless connection in your house you can look at 'home sharing' to access music across several PC's in the house instead.
I don't buy from iTunes it's much too restrictive BUT it's a good system for managing music. Amazon is very good for download costs and there are no restrictions about the number of copies you make