Medusa

Medusa is Papa Acahalla's wife in the Amsterville roleplay mod and Sally's real mother. Papa Acachalla constantly makes phone calls to Medusa about Sally, who was with him at the time. One phonecall was about how Sally probaly had brain damage, Sally commented on the call, but Papa Acachalla lied to her and said that she has "bran cereal". Later, Papa Acahalla divorced Medusa, and Medusa didn't fight for custody of Sally. Medusa is never mentioned again.

Sally and Acachalla
Throughout the Amsterville video, Papa Acachalla makes phonecalls to Medusa. In one call, it is implied that Medusa is Sally's real daughter, meaning that perhaps Sally is Papa Acachala's and Medusa's real, (and only), child.

Trivia

 * It was never said, but some think that Medusa is the same Medusa with the snake head that turns people to stone.
 * Medusa has not met Billy and Gertrude and is most likely not aware either.