Ruby was a holographic character from chapter 13 of the holonovel "The Big Good-Bye," who was one of Dixon Hill's "girlfriends."
When Jean-Luc Picard and Lily Sloane entered the holodeck on board the USS Enterprise to escape two Borg drones, Ruby approached Picard, who played Dixon Hill, dancing with Sloane, and passionately kissed him. She left after Picard asks her to leave, telling her that he'd meet up with her later. She advised Picard to "dump the broad." (Star Trek: First Contact)
Ruby was played by Hillary Hayes. According to the Star Trek Encyclopedia (2nd ed., p. 422), the character was named after the wife of
Star Trek: First Contact co-writer Ronald D. Moore.
In early drafts of the script, "Ruby" was the name of the character who would eventually become Lily Sloane.