Unfortunately I didn't manage to get a picture of this, but yesterday Nikki actually, of her own volition, jumped up on the couch and snuggled up against Brodie! At the time Matt and I were watching "Mythbusters" and Brodie was napping with his front half on my lap and his back half sort of curled up against my leg on the sofa. And at one point Nikki proceeded to jump up onto the couch, lean down, sniff Brodie's tail (which he didn't seem to mind at all), and then wedge herself into what must have been a cozy spot between Brodie and the inner surface of the couch-arm.
She's ended up in positions that look similar with both Brodie and Shadow in the past, but those have always been due to the boys managing to sort of "sneak up" on her and generally it hasn't lasted very long. But this was the first time I'd ever seen a clearly mutually-acknowledged-and-approved snuggle occur between Nikki and any of the other cats. And the two of them stayed that way for a good 15-20 minutes (15-20 minutes during which I was trying not to move for fear of startling them -- that's why I don't have a picture, as getting up to find the camera would surely have led to Cat Scatter).
Anyway this pretty much confirms to me that Nikki might very well be willing to make friends with Brodie, and that I was right about Brodie having amazing Kitty Social Skills -- he's such an impeccably polite gentleman-cat that not even a Cat of Little Patience like Nikki can manage to stay perpetually irritated by him. Which is just all kinds of awesome. Again, I'm happy just so long as the cats are civil to each other, but this is really nice to see regardless.