If Lizzy's telling the story among her friends is umbrage;
why are we told Elizabeth delighted in 'anything ridculous' , not by Lizzy but by the narrator ?
Elizabeth response of 'mortified pride' was a humourous exaggeration-- She has as much right to her pride as he does to his pride.
Elizabeth has more intelligence and self-confidence than to let a rude remark by a stranger affect her opinion of herself.

You say Darcy's remarks about Lizzy were excessive and personal, then say her reaction was not the best ?

At least she has her father's sense of the ridiculous !