I agree with SA and NM. You held your head high and attended the party with old friends. I grew up in a small town in Wisconsin so I know how everyone knows everybody else's business but you have nothing to be ashamed of. Your presence there spoke volumes to everyone about what a classy lady you are...........Think about how everyone respects Sandra Bullock's handling of her H's philandering. Well done!
I love the part about the ow waiting in a hot car. I'm guessing she let your H know how she felt later.
How close are you with SIL? Is she still being an aunt to your children?