Andy,

in my opinion the "slap" on the car is a rather mild version of the "screech-BANG" that could have been. She very nearly caused a severe accident, and she should be made aware of that. I also think she should be scared. Scared of her own lapse of attention (and not of the cyclist).

When this sort of thing happens to me, I want them to know it was a close call, and a slap on their car gets their attention better than anything. I do that regardless of age or gender. Quite often that is all that is needed, but I have gotten into a couple of (peaceful) conversations, where I have explained my position and sometimes my legal rights as well.

--J