"bjrutledge" said:
This doesn't make sense. Why do you need to provide a DNI of someone here?
As strange as it may sound to people from US or EU, she needs to get a tourist visa to enter the country. Not the one that is granted automatically at the border to the people from privileged countries, but a regular one you need to apply for, go several times to the embassy and stay in lines.
To get a regular tourist visa an invitation letter is required from a local resident with a DNI who will vouch for her, promise that he will be responsible for her expenses, that she will have a place to live during her stay etc.
If you book a hotel for the time of your vacation, hotel manager can assist you with getting such a letter, but she goes to Antarctica trip, so she needs somebody else to do it.