How does the opera singer die?

I've been watching this during the day, probably not the best time to do so, be it the sun reflects on my television, but I was wondering how the opera singer dies in the beginning of the film. I was wondering if I wasn't seeing the whole picture.

It seems like she just faints and then dies. But the info from my cable box says that the evil doctor murders her and then brings her back to life. I didn't see a flat out murder though. I mean, did she die of fright because she was nervous about the doctor being a stalker? Or did he do something, like poison or something like that to actually kill her.

I may watch the beginning again. I was sort of sleepy when I started so maybe I need to pay closer attention.