"I am sure there is not on his. I will answer for it, he never cared three straws about her -- who could about such a nasty little freckled thing?"

Elizabeth was shocked to think that, however incapable of such coarseness of expression herself, the coarseness of the sentiment was little other than her own breast had formerly harboured and fancied liberal!

Lydia has uttered two coarse expressions--
1. Wickham pursued Miss King solely for her money
2. Miss King is not a pretty young woman

Elizabeth had previously viewed Wickham's pursuit of Miss King in a tolerable manner. He was a young man who needed money and Miss King was "the" heiress of the Meryton neighborhood. Elizabeth does not say more than Miss KIng is a good sort of girl, but it is possible she held a similar opinion in regards to Miss King' s appearance, Freckles were considered an impediment to beauty in that era, I believe.

So Elizabeth is forced to confront another truth about herself, that she was not so far removed from Lydia's sentiments as she would have liked.