Three potential scenarios that creep in from time to time -
My hunch is that an obsessive fan of SG, likely unknown to her or her handlers, meticulously planned all of this because of a perceived slight/rejection. Planned potentially for years, but could've also occurred when she aired the "Coming Home" special highlighting her family and city.
Second thought is an old middle school/high school/college classmate, likely an introvert not really adept at girls (but a whiz in the classroom), who secretly idolized and obsessed over getting her attention. Likewise, a perceived slight or rejection occurred at some point along the way.
A girl, much like the classmate above, secretly longed for acceptance from cliques but it never occurred and never has occurred.
JMO.