] And even if she would fall well short of a perfect life's helpmeet, "sickly and cross" is easier for a husband to evade than energetic and domineering like her mother.

Yes, so long as Col Fitzwilliam found Anne unobjectionable, he'd be a fool not to marry her if he got the chance. She's probably worth at least twice the fifty thousand pounds that Elizabeth estimated to be the highest that earl's younger son was worth.

I think "sickly and insipid" or even "sickly and invisible" are more likely for Anne - but we really see very little of her.

] Picture having Lady Catherine for a mother-in-law, though. That's one case where marrying for money means earning it the hard way.

Not only mother-in-law, but live-in mother-in-law. As Col Fitzwilliam has no estate of his own, he'd presumably move in to Rosings. This would make Anne technically the lady of the house, but can you imagine her standing up to her mother over anything?