I'm not sure if the feathers would be real, but these would be coloured and worn in ther hair simply for decoration. I'm presuming you've not got a copy of P&P2 to hand, as this can be seen there. They stick up and make the sisters stand out too.

They have them and the Bennet girls, or any of the others, do not, because the Bingley sisters are very fashionable, spending plently of time in London. They also seem to have a reasonable amount to spend, although JA tells us they were in the habbit of spending more than they ought!