Most Helpful Girl
Be straight up and tell her that you don't feel like you two can work. Just let her know that you respect her and don't want to run her through the ringer by giving her false hope with something that just CAN'T happen. She will be hurt no matter what, but the straight up approach is the only way to go in my opinion.
Most Helpful Guy
You don't. It was 1 month. Tell her you are not interested and move on.