Someone who you might think is your friend, but is going to bail on you the moment you would expect them to uphold their end of the friendship; about supportive as a paper cut-out.
Unlike a real friend, a paper friend will never be there to cheer you up, bail you out of trouble, or help you out in any way, if they aren't getting anything out of the deal at least. Unlike a Theoretical Friend
, they probably never really were your friend in the first place.
"You don't need those paper friends at all, no you don't need those kind of friends."