Sally, or rather Sarah (for what young lady of common gentility will reach the age of sixteen without altering her name as far as she can?), must from situation be at this time the intimate friend and confidante of her sister.

Who doesn't know a teenaged girl who has changed her name (at least the spelling), or done it herself? It reminds me of the line in ch.16 of P&P where the Bennet girls are at their aunt's house and have nothing to do but "examine their own indifferent imitations of china on the mantlepiece" (presumably china they've decorated, not very well, and then gave away as presents to their fond aunt who then displayed them on her mantlepiece forever). Some things don't change!