"Post Mortem" comes from Latin, meaning after death.
The photos ”Post Mortem” apparently originated in England, when Queen Victoria asked to photograph the corpse of an acquaintance or a relative, so she can keep as a souvenir. Soon after, this idea spread around the world, keeping a morbid reminder of loved ones that have passed on.
Even today, as strange as it may seem, some places still have this custom. How horrific would it be to go through the process? You are morning your loved one and you have to pretend they are still alive while posing in your best dress? Not only that but now you have a reminder of that day. In some cases these would be the only pictures EVER taken of the relative.
The girl who is standing in the photo is the one who is dead.
Notice the hands. The greysih coloring is how you can tell the person is no longer living.
For people wondering how the corpse is standing up, there is a posing stand supporting the body it’s very hard to see but the stand is supporting the neck, arms and back. That is one goulish piece of patented stagecraft.
The girl in this picture has her eyes open, but in some cases the photographer will paint pupils on the eye lids to make it seem like they are wide awake. There was a whole production behind these pictures and at the dawn of photography it was all the rage. People wanted to preserve images of their loved ones and a sudden death made that all the more imperative. The first stop after death was not the mortician but the death photographer. It seems a gruesome way to make a living.