Richards was with Charlie Sheen hours before his hotel liaison with Capri Anderson. She was also across the hall from Charlie's room and went inside after the incident. And, we're told, Richards went inside the room and saw what could be evidence in the investigation.
We're told Richards has given assurance she will "fully cooperate."
Anderson went to the NYPD Monday and filed a criminal complaint against Charlie for assault and battery as well as false imprisonment.