If her husband had treated her right, IMO at least her nerves would be in better shape! I always figured that Mr. Bennet was hardly exaggerating when he said in ch.1 that his wife was as handsome as any of her daughters (though he made sure she couldn't enjoy the compliment for more than a few seconds!). I picture her as a very pretty and rather sexually appealing girl when young and still distinctly good-looking now (IMO P&P2 got that part right with Alison Steadman.) I agree that in personality she may have been very like Lydia. (Ooh, what does that say about what will happen to Lydia's general cheerfulness as she gets older, though?)-:

We are told in ch.1 that the Bennets have been married for 23 years, so that would make her at *least* 40, IMO. I picture her marrying fairly early, at 20 or 21, but not unusually early, such as 17. I agree that Mr. Bennet is the bigger fool for having married her, since he's supposed to be the smart one! (I'm reminded of a line from a PBS documentary I watched a long time ago about Caroline(?) of Brunswick, the wife of the Prince Regent. The two of them had a stormy relationship, and after her death someone said of her "In the hands of a sensible man who loved her, she might have turned out well." It strikes me that the same might be said of Mrs. Bennet (or at least, that she might have turned out *better* than we now see her!).