To get this trophy you need to complete a daily challenge that someone on your friends list has completed and try to beat their score.
It seems that you need to get them to show up on the "closest challengers" screen so that their ghost appears during your challenge. I found the easiest way was to get a score near someone on my friends list and then replay the challenge so I could complete against their ghost directly.
This trophy hasn't been working until today but the games' offical twitter account confirms the trophy has been fixed and should now unlock. Previously people were not seeing their friends ghosts during the daily challenge.