I once did a compilation of every reference to Elizabeth Bennet's physical characteristics and beauty (or lack thereof), but it took me till this GR to realize that Darcy changes his mind about her looks fairly quickly. At the Meryton Assembly in ch.3 he finds her "tolerable, but not handsome enough to tempt [him]", yet by ch.6 he is "meditating on the very great pleasure which a pair of fine eyes in the face of a pretty woman can bestow." As Elizabeth tells Charlotte at Lucas Lodge, at this point Jane has known Bingley for about 2 weeks - "She danced four dances with him at Meryton; she saw him one morning at his own house, and has since dined in company with him four times." I think we can assume that Elizabeth and Darcy have met on the same occasions as Jane and Bingley - they've seen each other 5 times since their first meeting, and by the fifth occasion Darcy definitely thinks she's pretty!