Isn't stating that Barbara and Helen are lovers enough to allude to the fact they're having sex? What more do you need to write about that subject? To me anything more would border on graphic sex and that's just not your style. Yours is a style I appreciate because you assume your readers are intelligent and I like to think we are. To extend that a bit, we can even imagine that Chase and Brandon do have arguments occasionally. It's not really relevant to the story though because ultimately, as you stated, this is not a relationship-based story. That's just the hook to keep us interested in the real story, that of The Scar.