What is ironic in the short story Johanna by Jane Yolen?

The reason why she couldn't see the deer behind her was that she was in fact the deer. This is why no one in her family ever came back from the forest; they were all deers. Since her family was cursed, her mother told her never to go in the forest without telling her the reason, so she did anyways and got transformed on her way to town to find help for her sick mother.