1.) Yes, I'm saying that there is a mistake on the tombstone. It's always possible that they didn't have the money at the time to get a stone. It usually takes at least a year or so to get a stone placed. There are at least three sources stating the bad date, NIS, the Fogle book that she walked herself, and the photo that I personally took. NIS is not wrong, Holdcraft only took the information that he saw, he was not interested in cross checking the stones with dates of death.
2.) I don't have any other information on Elizabeth so I don't know anything else except what I can find in NIS.
3.) I will be at the historical society of Frederick tomorrow and if the right people come in I can talk to them about the Slifer cemetery. I know the area, but I don't know where it is exactly.
4.) I don't know what the stone looks like, but Fogle, who did her work in the late 90s, said she couldn't read it. One would have to look back at Holdcraft's note to see where a mistake might have been made.
5.) I don't know anything about the Slifer family, I have come across the name before. I also have a good number of books on the Frederick area and I like to look things up.
I think that you are using NIS as something it's not. Holdcraft was interested in copying down the information on the stones of Frederick county. It is not meant to be a primary source, it's at best a third source since if you think about it since someone had to get the information from someone to make the stone, then someone else made the stone.
I can see plenty of reasons to make mistakes on stones, from a few years from burial to getting the stone, to replacement of the stone.
There are plenty of reasons for NIS to be wrong as well. As I've said he was supposedly going blind. He took his information into notebooks, then put them onto cards and then into the book. However, to say that he is wrong because the stone doesn't match what actually happened isn't his fault, that's a problem with the stone.
I do think that if someone finds something wrong in NIS it should be that the information differs from what the STONE says and not what actually happened. A note could be added saying the correct information as well, but don't change the fact of what the stone does say.