Gilda was a character in the original unaired pilot of The Big Bang Theory. She was played by actress Iris Bahr. Even though her character was scrapped with the unaired pilot, she was the prototype for the later developed character Leslie Winkle.
In the episode, when she finds Katie in their apartment, she becomes jealous because she has an interest in Leonard. Katie assures her that she has no romantic interest in the two geeks. Later, Katie takes them out to a dance club where all three of the geeks show some very unconventional dancing skills.