One library two computer, constant rescan?

Make sure that she connects to the iMac share before she opens iTunes.

 

Hello here's the solution I think will work for you.
First, you need to make sure that the MacBook is connected to the network.
By opening the drive your music is connected to.

Now, on the MacBook before you open up iTunes make sure you press and hold the "option" {alt} key and open iTunes. This will bring up a window asking if you want to use a different iTunes Library.

This will give you three options.
[QUIT] [Create Library] [Choose Library]

Click on "Choose Library" this will ask you to look up a folder with your "Library" file.
You will have to make sure that the volume where the iTunes music is on, that is OPEN, other wise you won't see any files. (We'll presume that this is how you have your file structure.)
Look into:

The iTunes folder should have a couple of folders and files.
The only ones you will be able to select are the the library files and the other folders.
select (look for) "iTunes Library" file. It will have the "mp3" icon. -- This is a "DATA" folder which contains your Database, [File paths, videos, movies {{Does NOT contain GAMES, this will be a different library file}}

After selecting your library it should start to sync your files.
Doing this procedure she should be able to add music to the library and so will you, as long as you guys set the advanced settings to "Keep iTunes Music folder organized" and make sure the path to your music folder is linked to the network folder or you iMac.
Also "Copy files to iTunes Music folder when adding to library" should be selected.

This way you guys can share the same files and sync multiple iPods/iPhones or whatever. But make sure both Computers are Authorized to play the files. Otherwise you will be able to play them but not your wife.


Hope this is not too confusing, and I was able to help.
Let me know if this doesn't work.