Well this is obviously AVG's fault to properly uninstall but I'll try to help:
1. First search the registry for all occurences of the word Grisoft (I'm assuming the installation path of AVG had this word in it) and delete them,
2. Next quit Outlook and search your system drive for all occurences of a file called "extend.dat" and delete all those files. If you're afraid to delete, you can just rename or move them to some other location - the point here is that they must not be found at their current location.
Hope this helps.
Greetings to your wife,
Vlk