she's saying there's a fundamental incompatibility between someone who wants BDSM and someone who doesn't that's impossible to resolve

Exactly, and that bothers me because you know whose relationship involves someone who's into BDSM and therefore also has a partner who's into that? Mine. I'm in a triad with another woman and a man, and my girlfriend is into BDSM whereas I'm not, so she and our boyfriend do that stuff. It's not any harder than any other relationship if you actually, y'know, communicate.