Thanks for all the responses, everyone. Ilrag, you didn't make me feel like an idiot, I was making myself feel like an idiot by stressing over something so trivial. I'm not usually so emotionally responsive, but there was a time in my past where there were a lot of drama llamas who delighted in stirring up trouble, so I guess I'm a little hypersensitive to these things.
I ske with DF over dinner (twice-baked potatoes, yumm!) about what was said. I approached it from the standpoint that her attitude seemed very odd for her. I told him what was said, and that I believe he had been honest with me. His response was apologetic that BW was acting out of character. He said that a little over ten years ago he and BW were the single ones in their circle of friends, and that led him to pursue her as girlfriend potential. She turned him down. They've been friends ever since.
He offered to take her out of the party if it made me uncomfortable. I suggestd that she is likely feeling left out as the only single girl in our circle these days (even her younger brother is in a long term pairing) and perhaps just speaking out of character. The wine didn't help either. I closed that I didn't need a blow by blow, but rather a little reassurance that it's OK to be concerned with what she said.
He followed that up with showing me his Social Security report from the last 15 years. Lol