How we cite our quotes: Citations follow this format: (Chapter.Paragraph)
Quote #1
"I assure you," said she, "I would not stand up without your dear sister for all the world; for if I did we should certainly be separated the whole evening." Catherine accepted this kindness with gratitude, and they continued as they were for three minutes longer, when Isabella, who had been talking to James on the other side of her, turned again to his sister and whispered, "My dearest creature, I am afraid I must leave you, your brother is so amazingly impatient to begin." (8.2)
There are lots of different kinds of lies in this text. Here Isabella exaggerates her desire to stay with Catherine, then promptly turns around and ditches her anyway, which turns her earlier "kind" sentiment into something hollow.
Quote #2
In this common-place chatter, which lasted some time, the original subject seemed entirely forgotten; and though Catherine was very well pleased to have it dropped for a while, she could not avoid a little suspicion at the total suspension of all Isabella's impatient desire to see Mr. Tilney. (8.21)
Isabella has a habit of saying things that sound very nice, but that she doesn't mean. Isabella might not be actively lying all the time, but her white lies, exaggerations, and omissions really start adding up.
Quote #3
Catherine listened with astonishment; she knew not how to reconcile two such very different accounts of the same thing, for she had not been brought up to understand the propensities of a rattle, nor to know to how many idle assertions and impudent falsehoods the excess of vanity will lead. (9.31)
John's "idle assertions" point to his carelessness with what he says – his ultimate agenda is to serve himself, not to say things that are clear or even true.