If she's using Outlook for email and want to stick with it, I can recommend the SpamBayes Outlook plugin.
See [link|http://spambayes.sourceforge.net/windows.html|http://spambayes.sou....net/windows.html].
The page does provide for a way to make Spambayes work with non-Outlook clients.
I have to use Outlook at work, and Spambayes helps to filter out the junk.