I think what the OP observed was an F/A going a bit overboard with professional courtesy. It has nothing to do with them being "friends". It would be quite rare for them to have even known each other. It's the same even when the non-rev passengers would for a different airline. I once had a Lufthansa F/A bring me a business class amenity kit on a FRA-BAH leg on which I was traveling, in-uniform, as a paid revenue passenger.
The problem is when the F/As do this in a way that is not discrete. It should not be noticeable to the other passengers and should not affect the service that they receive.