Summary of District of Columbia Gun Laws
Washington, D.C. is a shall-issue district with concealed weapons permits issued by D.C. Metropolitan Police.
All firearms must be registered, and this process acts as a permit to purchase. Individuals cannot possess ammunition without a valid registration of a firearm.
Open carry is illegal in D.C.
District of Columbia Concealed Carry Pistol Licenses (CCPLs) are required in order to concealed carry and are issued to residents and non-residents and require a firearms training course that has been approved by the Metro Police. You must be at least 21 years old to get a concealed carry permit in D.C. Any firearm you plan on carrying in Washington D.C. will also need to be registered in the District. In addition, possession of ammunition for an unregistered firearm is prohibited in the District of Columbia. Some areas are off-limits even with a D.C. CCPL, including schools, public memorials on the National Mall and along the Tidal Basin and the area around the White House. In terms of reciprocity, Washington D.C. does not honor CCW licenses from any other state.
https://www.usconcealedcarry.com/resources/ccw_reciprocity_map/dc-gun-laws/
So she cannot open carry the way she does in Colorado and she would have to get a DC concealed carry license AFTER she takes their course. I doubt she has met those requirements.
Just to be sure she is safe, the DC police should pull her over and check that she is not illegally carrying or has any ammunition for a gun not registered in the District.