This is Shannen's bonafide Myspace page:
http://www.myspace.com/shannendoherty
This is 100% authentic because Shannen says so herself at the end of this (very enjoyable) video:
http://www.myspace.com/thefit
(Note: I assume 'thefit' changes the current video frequently; Shannen's is up on June 5 2009; on later dates you may have to search for her vid)
Shannen has no friends listed on MySpace so I assume she decided not to take any? Or maybe she hasn't weeded through applicants yet? In any case -- you might as well ask! Support Shannen!