I wonder why JA bothered with Mrs Hurst? Perhaps we are to see her marriage as an example of what Caroline might end up with if she doesn't find a rich husband who has an estate?

I do think you have a good point about Caroline & Louisa Bingley both having received a uniform education. Perhaps they were always similar in outlook, and their similar educations re-inforced that. I am still amused by the fact that Mrs Hurst is almost as much engrossed by Mr Darcy as Miss Bingley is -- Mr Hurst definitely doesn't seem to get much of his wife's attention. :-)