From what I can learn, the attack began with a feeling of drowsiness. In a few hours, she passed into a coma from which she never awakened.
10 seconds sound clip from the Revenge of the Zombies (1943) movie soundboard.
You can hear this line at 00:05:09.192 in the DVD version of the movie.
Quote context
[...]
- I came as soon as I received your wire. It was a shock.
- I feel quite sure of it. The circumstances were too suspicious to be ignored.
- Very.
- I met her only the day before, and she seemed well then.
- I made a determined effort to see her, but Dr. Von Altermann refused me permission.
- So what could I do? He was her attending physician, as well as her husband.
- Refused you? But you've known Lila all her life.
[...]