Disclaimer:
The story-line is mine. The rest of things are not. Is that enough of a disclaimer? I hope so.
Kitty, surprisingly, is the last. She begins to cough more and more, and Mr Jones advises them the sea air as a possible cure. So, they go to Brighton when the weather allows for traveling. Mr and Mrs Bennet are dubious about the trip, they remember what a disaster was the last one, but since they cannot, apparently, stop the inevitable neither in Longbourn, they allow the trip.
It is may and they are in full mourning, but Kitty's health cannot wait. They go to the sea, and for a while it seems to help. Kitty is breathing slightly better. They are not louder her than in Longbourn. If anything, they are a bit more silent, since Kitty coughs less. But here they are surrounded by noisy neighbours, activities and a city that thrive in the summer months. They hear laugh and music and joy, and that helps lift their gloomy spirits as much as the sea air.
Life goes on, and at the end, the Bennets spend their whole summer at Brighton. They have made some acquittances, but in stead of going each on their own way like before, they spend as much time together as possible. Mr and Mrs Bennet barely left Kitty out of their sight. A more attentive family to one another can hardly be found.
It is in their last week, when people has begun to left Brighton back to their own states, when the Bennets decide sail. Boat tours have become a popular thing in the last years, and it allows to see some strange creatures, like seals and dolphins. Kitty is entranced, and can barely wait to arrive home and draw all these creatures. Mrs Bennet only realises that Kitty has leaned out too much when she falls. As quickly as possible, they have her back in the boat, in part thanks to the playful dolphins, but not before she has breathed some of the salty water.
They decided to call it a day, and set room back to the shore. When they arrive to the house, the doctor is called, and he determines that Kitty is well. It only seems like a fright. During the following days, her cough has come back, but nothing worse that that seems to have happened.
When they finally head home, they do it making sure to stop as much as necessary, and to always put Kitty next to the fire. For some reason, this does not seem to help. She is wasting away, but unlike Mary, it seems to be because only physical, which in some ways is worse. It is as if her lungs cannot get enough air, but at the same time they are unable to keep breathing. Her cough comes back with a vengeance, and Kitty each day has more problems to breath. Mr and Mrs Bennet has resigned all hope to see their daughter live to see another week. Nobody is able to do anything. When Kitty finally leaves this world, it is in a day whose date coincide with that in which Jane was invited to Netherfield to dine with Miss Bingley and Mrs Hurst.