why does elizabeth question mr.darcey about his character? how does elizabeth treat caroline bingley when she"kindly" warns her against wickham?

Elizabeth is suspect of Darcy ever since his snobbery at the original dance. Elizabeth is looking for an excuse to condemn Mr. Darcy. Mr. Wickham's story confirms her prejudice against Darcy. This is why Elizabeth will have nothing to do with Caroline's warning against Wickham.