Sherry Johnston (arrested junkie) and Sarah Palin's supposed future mother-in-law was under Secret Service protection during the election campaign

It says nothing there about "the mother of your daughter's boyfriend." So why was Sherry Johnson under the protection and/or surveillance of the Secret Service? Did George W. Bush authorize her to receive this protection? And why would this unusual Secret Service protection prevent issuing of a warrant if the Alaska state troopers had reason to believe a crime was being committed?