After an initial web search (or ten), I was not able to locate info for this online. There is a car show in Kirkland that day, but it is put on by the "Legends Car Club" and appears to be focused on Classics & Hot Rods.
Info I found:
When: July 20 10:00 a.m.–4:00 p.m.
Description: The Legends Car Club welcomes all Hot Rods, Customs, Classics, Vintage, Muscle Cars, Trucks and Motorcycles. There are fun awards, raffles and trophies awarded in 21 classes.
Where: Downtown Kirkland
Contact: Dick Beazell at (425) 893-8766
There web site is: http://www.legendscarclub.com/car_shows.htm
Again, this is put on by a classic car club...so I'm not sure if they are what your girlfriend was talking about or not.
If it is not this one, and there is a Green Car Show going on at the same time as this large car show, I can tell you why we haven't heard about it....because they don't have a web site talking about it! (not that I'm biased to the internet or anything nnww).
Let us know if you find anything more about the specifics of this. It is possible that whoever organized this is trying to get some overflow / bleed a little traffic from the established Car Show....but I have the feeling that perhaps the communications got mixed somewhere and there probably isn't a Green Car Show that particular day in Kirkland.