As a European (though I did spend 27 years in NorCal) I worry that US pop culture is too readily absorbed over on the other side of the Atlantic and with it all the tedious baggage of US sexual repression and concomitant anxiety and dysfunction.
Your opening question regarding what word would pop instantly to mind upon learning that a woman has slept with 4 men in the preceding 12 months was, for me, “conservative.” I’d assume she was either too anxious about sex or too busy working all hours of the day & night to have had more lovers.
To put this into perspective, some years ago I enjoyed a multi-year cohabiting relationship with an intelligent, self-confident, and sexually mature woman. In our first year together she had an average of 2 new partners per month, most but not all of which were men. Things didn’t change much in the subsequent years. We were both busy people, and of course many of her lovers were frequent visitors, otherwise no doubt we’d both have had a greater opportunity for discovery, learning, and pleasure. Our relationship ended for a variety of reasons (children, location, a failed startup), none of which had much to do with sexuality or jealousy.
I’m glad to see more people are writing intelligently about human sexuality. It’s varied, it’s fascinating, and it’s not amenable to being constrained by silly rules invented by people who are frightened of it. The more we relax and just explore to see what things work for us as individuals and what don’t work for us, and stop trying to tell other people what they “should” be doing and feeling, the better off everyone will be.