I did eventually give her a hug, and hold her a bit. But yeah, after screwing another guy for more than 3 months, all the while knowing that I knew, her kids knew, and he parents knew, I did have the "cold" shield up, full-force.
I had to protect myself, and still do, as we haltingly move forward together in fits and starts. We have since hugged and touched quite a bit, all of it coming naturally at the moment. Just as that "cold" moment that you mention seemed genuine to me at that time, so too does the greater affection now as we share it.
