What happened was: first, Quinn took a sideways stance where her back would be against her 6-foot staff, same hand still in the same position, but her free hand was now almost at the other end of the stick—though it wasn't visible from Roxanne and Melina's POVs. Furthermore, the way the stick was positioned was relative to how each of them was looking at the end of it.
To give a much simpler explanation, Quinn looked like she was doing some sort of trick shot while playing billiards while the two could only see the "circle" of the end of the stick, a fraction of a second before they got hit.
With that said, after Quinn took that stance, she relaxed her grip on the end of her stick before she used her free hand to violently push it all the way, then retracting it back after making contact as if nothing happened. However, what exactly happened after that was leave a perfect circular imprint on Roxanne and Melina's foreheads that hurt more than a simple finger flick could do.