I agree about the extent of Lizzy's Darcy-baiting. She does seem to be doing less of it than in Hertfordshire. Perhaps the reduction came even earlier? When they danced together at the Netherfield ball, she first tried silence -- with the outward appearance of non-hostility -- before suddenly fancying that it would be the greater punishment to her partner to oblige him to talk --ch18. That shows a less chirpy state of mind than, say, the time she breezed off from Mr Darcy and the Binglettes in the garden ("... The picturesque would be spoilt by admitting a fourth. Good-bye." --ch10). In that case, the probable reason for the change is Mr Wickham's story and her reaction to it: "I had not thought Mr. Darcy so bad as this -- ..." --ch16. Also, a fair share of her chirpiness in Kent is directed at a worthier object: the colonel.