I was at that show. It was the Sunday show the day after the Oakland incident. Robert dedicated the next song to Bill Graham then they started playing No Quarter. During the middle section this lady comes out on stage dancing. Robert for a few seconds dances with her. I never saw her on the piano dancing.
A few days later, Graham was on the local radio station explaining the whole ordeal. He said that he sent her out on stage.
I knew something was up that day, because we waited about 3 hours after Rick Derringer finished. Graham kept saying there was a problem with Jimmy's doubleneck.