what change in madelines condition occurs shortly after the narrators arrival

Basically she becomes sicker than she usually was and died soon after,

"She succumbed (as her brother told me at night with inexpressible agitation) to the prostrating power of the destroyer; and I learned that the glimpse I had obtained of her person would thus probably be the last I should obtain -- that the lady, at least while living, would be seen by me no more."