Expanding the existing army category to include civilian awardees is a simple solution so a new category would not be needed.
The existing category text indicates:
"The Distinguished Service Medal (DSM) is a military award of the United States Army that is presented to any person who, while serving in any capacity with the United States military, has distinguished himself or herself by exceptionally meritorious service to the Government in a duty of great responsibility. The performance must be such as to merit recognition for service that is clearly exceptional. Exceptional performance of normal duty will not alone justify an award of this decoration."
Hannah, never served in the military. Perhaps the individual who created the category may not have realized that civilians can also receive the awards.
Language could be added to the existing Army category to indicate that "The DSM can also be awarded to civilian awardees who provided exceptionally meritoriously service to the Government." unless there is a desire for separate categories to recognize military vis-à-vis civilian recipients.