member of TWO NPC sororities

[KappaMe]

Hey everyone,
I browse through greekchat often but haven't posted. Anyways, my sister is a member of a top tier NPC organization at her school. Recently, she heard about a girl who is in the pledge class under her, who has been a member for over a year, was a member of another NPC organization at another school before transferring to her school. In addition, some girls in the sorority knew of this BEFORE rush, but apparently felt that she was so desirable that they still let her join. Likewise, this isn't a case of moving clear across the country, the girl's original school is only a couple hours from her new school (the one my sister attends). Now, most girls in the sorority know of this, but don't feel it is necessary to do anything since she's been such a valuable member for so long. And to make matters even worse the girl's original sorority is at her new school. So why couldn't she just transfer chapters?