If she had intended to write it in a word document on her computer but instead accidentally wrote it into her email client and sent it to a random person, I'm not convinced she would escape getting charged then either.

It's not any different than telling an automated phone voice tree system that you plan on killing someone and then being surprised that your words were later heard by a human. She absolutely told a company's computer. She sent the message.

The law may have been intended for more direct threats to a person as a means of intimidation, but that's a separate conversation.