I simply don't know why this film gets a rating of 6.4 out of 10 on IMDB. Let's Scare Jessica to Death has a great title going for it but nothing much beyond that. It is quite slow in its pacing and feels long even though the film is listed with a run time of 89 minutes.
There are a number of great early 70's horror films. This is not one of them. The acting is uneven and poor at times. The way that Jessica runs in terror through the field makes one wonder if she has any muscles in her legs at all. I know it was the Seventies but, come honey, you can run with a little more determination than that!
I just found this film rather dull and hardly suspenseful at all. The basic story centers around Jessica who just got out of a mental hospital and is desperately trying to hold onto her sanity. While the movie is nicely moody and atmospheric at times, this is about all it has going for it.
The vampire angle is a bit interesting but, again, they don't do much with it. I have to disagree with the majority of people on this one and say "Ho-hum." If you want a nicely crafted horror movie from the early 1970's try Black Christmas (1974) or Deranged (1974).
For more info check out the film's entry in IMDB.