Canadian, currently with US green card living in Canada

My wife is a Canadian with a US green card living in Canada.  We're both retired and she has US SS and a US retirement (CalPers) income.  Currently we file in both Canada and have filed jointly in the US.  However, my  wife will be getting a large Canadian capital gains distribution.  Does that need to be declared in the US or is it only my world-wide income that needs to be declared in the US.