As we know from Chapter 4, "On the strength of Darcy's regard Bingley had the firmest reliance, and of his judgmeent the highest opinion." Darcy probably had only to say to Bingley on their return from Meryton and the encounter with Wickham that he questioned the wisdom of including him in any invitation because of the previous "infamous manner" alluded to by Caroline of their earlier relationship. We don't see any evidence of Darcy having revealed the whole of the situation to Bingley, but in light of their friendship there was probably some discussion, and definately only what was necessary was relayed to Caroline.