GSUSA recommends 12 as the best size troop to allow girls a complete Girl Scouts Experience.
GSSNV, per Volunteer Essentials requires:
8 girls in Daisy, Brownie and Junior and multi-level troops.
5 girls are required for Cadette, Senior and Ambassador troops.
Troop not meeting GSSNV minimums should be displayed in the troop catalog for new girls to join until meeting minimum.