I agreed that Caroline's marrying an American was surprising. But really, with her brother marrying Jane Bennet, what else is a vain, selfish and catty singleton to do? ;-)

First of all--and most importantly, I think--this wedding marks the end of her tenure as Lady of Netherfield Hall. Jane supplants her--though it's a bit silly to think of Jane's supplanting anybody, as she's so invariably gracious--and she is reduced to the condition of a spinster sister. She doesn't have to stay at Netherfield to see Jane take over. But how much better than that is the Hurst's house in Grosvenor Square? She's still second to her sister, and to a sister whose husband has "more fashion than fortune" and is not the most interesting person to have about the house. In his own home, I'd expect him to be even more indolent than at Netherfield, if such a thing is possible.

My take on it is that Caroline latched on to the first man she could get, just to get out of her siblings' houses and into one of her own.