Crossing Guards or Traffic Cops?

Crossing guards serve a very important function - protecting our children on their way to and from school everyday.  But at least one of them seems to have appropriated another important function. 

This guard (and I will stop short of identifying her) has taken it upon herself to conduct traffic at her intersection during the morning rush even when there are no children present.  She stops vehicles that do not have a stop sign from proceeding and allows vehicles on the cross-street to proceed across and ignore their own stop signs. 

Maybe I'm just ignorant about this, but I didn't realize that was part of a crossing guard's job description.   Maybe someone could enlighten me as to when a crossing guard crosses the line from helpful to harmful?