Disco Freeze
Play disco music and have the girls dance around the floor, displaying their disco moves. Assign several adults to supervise the dancing contest and judge the results. When the music stops, all the girls must freeze in place; anyone moving will be eliminated from the game by the judges. Once the eliminated girls have exited the dance floor, turn the music back on and continue in this pattern. Play the music in varying intervals, from a few seconds to a full minute or two. The last girl still standing wins the contest.
Disco Dance-Off
See how long the girls can demonstrate their disco moves. Play the disco music; you can even play a disco movie such as Saturday Night Fever or a show with disco choreography such as Fox's So You Think You Can Dance in the background for inspiration. Be sure the music playlist is long enough to keep the girls dancing for an extended period of time. The last girl dancing wins. Depending on the participants' ages, this game could go on for minutes with younger girls or even hours with an older group. Turn the game into a charitable endeavor by having the girls collect sponsored pledges, such as $5 for every 10 minutes danced, prior to the event.
Disco Memory
Assign an adult or experienced dancer to serve as the leader. Teach the group of girls one disco dance combination at a time. Once they learn one combination, have the girls perform it back. Add on another combination; the girls must then perform back the first and second combinations in sequence, and so on until they have completed an entire dance. When girls forget the steps, they are eliminated. The girl who learns the most consecutive disco dance combinations wins the game.