After having to listen at the Netherfield ball to Mrs. Bennet rattle on and on about how sure she was that Jane would soon marry Bingley and how rich she would be, and after all Mrs. Bennet's saying that Charlotte is plain and Jane is beautiful, Lady Lucas is enjoying her chance to gloat a bit. When she talks about the comforts of having a daughter well-married, I wonder if she even throws some of Mrs. Bennet's own words back at her. I can't say I blame Lady Lucas for seizing the chance to boast a bit. And she may have thought Charlotte would never marry, so she can't be blamed if her happiness overflows a bit.