] I don't at all think Caroline thought she was being helpful; in fact, it makes me wonder why she said anything at all. If Caroline wants Darcy to look down on Elizabeth, what better than to play up Elizabeth's presumed attraction to Wickham?

Darcy already looks down on Elizabeth. He doesn't need encouragement from Caroline.

] It seems that Caroline does the wrong thing again, with regard to the Caroline-Darcy-Lizzy triangle.

I don't think that Caroline sees a triangle. (And at this point there isn't one.) She believes (and so far she's right) that Darcy would not lower himself to marry this country girl with the low connections. She just enjoys scoring off Lizzy. If she does the "wrong thing" here, it is that the only evidence she presents is Wickham's descent (compared to Darcy's presumably). Of course, that's probably all the evidence that she has.