The BoB is accounted for differently than the alcohol...and technically isn't supposed to be comp'ed. However, the Purser has the power to comp items (for the already mentioned cases of a F pax not liking the F meal choices, etc.) While augmenting a FC meal choice isn't really "allowed" I cannot think of anyone I've flown with who wouldn't have just grabbed a bag of chips as long as the pax requested them nicely. (If they we're "demanded" it might be a different story.)

Without knowing all the circumstances involved, it does sound like this Purser was just being difficult.