Why does the old woman in the film The Survivalist die?

Question

In The Survivalist, why does the old woman in the film poison herself and die?

Answer 1

The old woman doesn't poison herself. She asks the girl to poison the man (since food is scarce), but the girl is in love with the man (and pregnant with his child), and she knows her mother is old anyway, so since food is not enough for three people, she decides to kill her mother with the mushrooms. When the mother realizes this in the morning, she accepts her fate.