I have been searching online sporadically for about 10 years to find this movie and only found your message board tonight. I have been trying to find a movie from my childhood for a long time now, likely late 70s early 80s. The only thing I remember from it is at the very end of the movie, a woman digs her way out of a dirt grave, in a rain storm and wearing a satin nightgown. For a long time I thought it was the made for TV version of The Fall of the House of Usher, with Robert Hays, and have watched every other version, as I have been unsuccessful at finding this version, but having seen all the other versions, no longer think this might be the movie. Let me know if this significant lack of details is enough to go on, seems like there are some miracle workers out here.
My dad woke me up as a kid to watch scary movies, and this image really stands out to me, it was on television, and I remember seeing that ending scene twice for sure.