had met at least a couple of times prior to the Lucas party. Mixed company invitations (like dinner) that included Bingley probably would have also included Darcy. So that would be four dinners where Elizabeth & Darcy were both present (same as for Jane & Bingley).

I'm not sure about the morning visit (that may have been when the Bennet ladies visited the Netherfield ladies for the first time). Bingley was present, but maybe he was already interested enough in Jane to make sure he was present. Darcy might have absented himself in this instance.