I have heard this used in relation to people that spend their life chasing luxury items or cool exciting technology (I'm a programmer), keeping up with the Jones's as it were. A reference to a more Buddhist way of life where one should pay more attention to the simple things in life and less attention to luxuries. No amount of luxuries will fill a hole in your heart. The simplest things in life are the ones which will bring true happiness.
I can't speak to the context in which it was used, proverbially speaking it would have been related to what you were discussing, or some manner that she perceived of you.
I would wager that you did or said something where she perceived you were chasing costly details (luxuries) that she considered less important in the grand scheme of things - the cheese, where you should have been concentrating on the 'low hanging fruit', those things which are quickly, cheaply and easily fixed and give the greatest return on your investment - the bread.