We've talked before about how Louisa kind of molded herself to be what she thought Captain Wentworth wanted her to be - he admired firmness of character and so she became very obstinate about getting her own way.

Now, after her fall, she is "altered."

"Yes, I believe I do; very much recovered; but she is altered: there is no running or jumping about, no laughing or dancing; it is quite different. If one happens only to shut the door a little hard, she starts and wriggles like a young dab-chick in the water; and Benwick sits at her elbow, reading verses, or whispering to her, all day long." (ch 22)

Now, I truly do believe Louisa has been through an ordeal and her nerves are not what they were. But how much of her present behavior is actual, and how much is what she thinks Benwick expects of her? He sits quietly with her and talks with her - he wants to take care of her (as he couldn't take care of Fanny?) and so Louisa is quiet and sits with him and lets him take care of her. If Benwick wasn't there being so solicitious of her tender nerves, would her nerves be more recovered? Would she, not be running and jumping about maybe, but be more active?

I don't think Louisa is consciously pretending weakness, but I do think she has a very malleable and pliable character, and unconsciously is being what her man expects of her.