Some people just assume everyone is on the forum and wave at each other all the time
The lady may have been puzzled to see another Coupe on the road, but wondered what you were waving at
I've seen a few Coupes around, but by the time you realise it's another Coupe and try to wave/flash, etc, it can be too late
I'm sure I've nearly crashed a couple of times, by looking back and trying to give an acknowledgment signal to another Coupe driver
Some people don't know that you are 'supposed to wave at each other'
My Mum doesn't wave to anyone she sees in the same type of Toyota as hers, as she doesn't know what make and model car she's looking at most of the time
If she's out and about in her motorhome though, she waves to all the other motorhomes she sees