2 people booked on a one way. One person needs to cancel.
As stated above, assuming this isn't an E fare or an Amex cert, you can split the reservation and cancel yours to retain the value of the ticket minus $200 that must be flown on one year from ticket date of issue.
In my experience, delta is willing to entertain any reasonable excuse as to why you can't make the flight. I've never paid a change fee....