Mary, at the end of a long concerto, was glad to purchase praise and gratitude by Scotch and Irish airs, at the request of her younger sisters, who, with some of the Lucases, and two or three officers, joined eagerly in dancing at one end of the room. (Chapter 6)

Unfortunately I do not think there is a great answer to be had at this point in time. There has been little opportunity so far to evaluate the relationship between the two oldest and the three younger sisters which might show influence—I can think of nothing which states this directly. For the most part we have seen the sisters in social situations where their actions are described as part of a montage of activities and not actual interaction with each other. In general, Lizzy and Jane might have had influence over their younger sisters just by being an example, as older sisters generally are but what affect they have had on them can only be speculation. For example, Lizzy is certainly lively and amiable and so is Lydia but which of these characteristics comes from influence not only from Lizzy but others and what is innate to her character. Of course to be influenced you also have to be susceptible to be influenced. The reactions of Kitty and Lydia in Chapter 7 to Mr. Bennet’s criticism might give us at least one clue. Kitty was disconcerted suggesting she is more open to influence while Lydia is perfectly indifferent suggesting she is not so open-minded. The only direct interaction between the sisters up to Chapter 9 that I can immediately recall illustrates aspects of their relationships to me rather than of influence. The conservation between Lizzy and Jane in Chapter 4 about Bingley show they have a good relationship and although they are different they seem to appreciate those differences and care about each other. It was interesting to note that Mary willingly plays music for dancing in Chapter 6 which shows she is not as querulous as portrayed in P&P2; it also shows the reverse that Lydia did not care so little for Mary that she interrupted her performance to demand a jig. Kitty and Lydia's whispering in Chapter 9 show they are rather close. A general observation on the sister’s relationships besides the division between the older and the younger was that there did not seem to be any discontent between them. The question of influence on the younger sisters is an interesting one and I will continue to look for clues. ;D