She is located in the basement of a ruined house south-east of Red Rock Canyon.
Close to the Spring Mt. Ranch State Park, the building is a destroyed, wooden-framed house at the entrance to the canyon. Look for the brownish-yellow storm door covering stairs that go down to the basement.
This same difference in vendor inventory lists also means that the Great Khan armorer will sell very high amounts of most ammunition, up to several thousand units depending on the type. Although these are very high amounts, they will be only half of what Quartermaster Bardon will stock on average.
She won't become hostile if the Courier is wearing NCR armor. The same also applies if Boone is in the player character's company.