This is
Just Like That ...? by the illustrious Pam Jernigan.
"Back off, Linda. He's taken."
Clark Kent stared at his partner, dumbfounded. Had someone kidnapped Lois Lane and replaced her with Cat Grant while his attention was distracted?
If there was one thing he'd depended on where Lois was concerned, it was that she would never lay claim to him openly like that. That was the whole point. Sure, she hated that Linda was flirting with him, making obvious her availability and willingness. But Lois was supposed to react the way she'd done time and again over the past couple of days: a façade of rolling-eyed irritation about the fact that another woman was coming on to him, together with insistent denial that she was feeling anything even remotely close to jealousy. Yet at the same time she would find excuses to snipe at him. Open hostility towards Linda, both to the other woman's face and to him, was also to be expected, together with an undercurrent of possessiveness - but not, of course, because Lois was jealous.
