The authority cited — 'Lady Catherine herself says' — is the person least qualified to give an objective assessment: the girl's own mother. Collins presents this biased source as though it were an independent authority, revealing his inability to distinguish between rank and truth. The phrase 'in point of true beauty' adds comic emphasis: Lady Catherine claims access to a higher, more authentic standard of beauty unavailable to ordinary people.

The superlative 'far superior to the handsomest of her sex' is an absurd hyperbole — Miss de Bourgh is described elsewhere as pale, thin, and sickly. The gap between Lady Catherine's claim and reality creates bathos (a comic fall from the elevated to the ridiculous). Austen lets the absurdity speak for itself — no narrator commentary is needed.