If you're not using an MS Exchange server (like me) I don't think you can use the redirector to select specific folders to forward to the BB. Instead, from the BlackBerry Desktop Manager, select 'Redirector Settings' and set up your forwarding needs from the 'Filters' tab.
For instance: (after getting to the 'Filters' tab as mentioned above)
Suppose I want all mails from
to go to my BB, but all others to stay put. Create a new filter (click on 'New) give it a name 'Wife Filter' check the box 'From:' and put in
make sure that 'Forward message to the handheld' is selected then click 'OK'. Do the same for
then here is the important step. Still in the 'Redirector Settings' dialogue, below the filter names there is a box 'When none of the above rules apply' - select the "Don't forward messages to the handheld" then 'Apply' 'OK' and you *should* start getting just the emails you want sent to your BB.
Hope this helps!