The agents are correct, as are the other posters. Unfortunately, rules are rules and these particular rules can not and should not be bent. First of all, if you check luggage in your Fiancee's name and then for whatever reason she does not make it to the airport, traffic jam, accident, delayed meeting, whatever. The luggage MUST be taken off the plane. NW will not take off with luggage on the plane if the passenger is not on the plane unless NW removed the passenger ( ie. Denied boarding). I think this is a security mandate and is called Positive Luggage Match. I also think that you were misinformed that it would not be a problem if you were both on the same PNR. It might be less of a problem, but there is still the issue of checking the ID of the person physically checking the luggage.

You have the other issue that Boston was actually an airport where some of the attacks were launched. I would hope that they are cautious with potential problems there.

All luggage must be checked 30 minutes prior to the flight so that it can be screened by TSA. You can ask the agent and it is possible that they will accept it. However, they are putting their job on the line and a considerable expsense to the airline if the luggage has to be pulled just to accomodate someone that bought a ticket and did not plan enough time in their schedule to catch the flight.

I am sorry, but your lack of planning or scheduling does not constitute a valid reason in my mind for the agent to take the risk of violating the rules/law. You might want to look into later flights and the possibilty of stand by.

UPS or a freight service might be another option if you don't want to risk missing the flight.