Srimati Radharani is described as the Shakti of Lord Krishna in the Brahmavaivarta, Devi Bhagavata, Skanda, Padma and Narada Purana and is worshipped along with Krishna by Parashurama and Ganesha in the Brahmanda Purana.
This Facebook post describes the story of Radha defeating the demons Harshana and Marshana, who are sons of Kalanemi. A short summary is given below:
Once there lived a demon called Kalanemi who had two sons named Marshana and Harshana who had assumed great power by chanting some secret mantras. By their powers all Devas, Gandharvas, Yakshas, Kinnaras, Guhykas and human beings were tortured by them. Everyone was afraid of these two demons. Unfortunately at that time none of Krishna's incarnations was present on the planet earth. Thus the devatas were in a very dangerous situation. Accepting Kartikeya as their commander-in-chief they declared war on these two brothers. These two demons easily defeated the devatas and rendered them powerless. Ranarangini Kalika Devi along with her many yoginis entered the war but they also got defeated.
Later the devas seek refuge of Shiva who tells them that as they are protect by the Vishnu Kavacha, only Radharani can save them.
The devatas immediately followed his instruction and rushed to her along with Lord Brahma and Lord Shiva. They went to the entrance of Goloka, where Radharani lives eternally, and chanted shruti mantras. Radharani was pleased with their prayers and invoked Sudarshana in Her mind and the chakra came before Her. Srimati Radharani ordered Sudarshana to go and kill Marshana and Harshana which he immediately did.
This story is said to be taken from the Brahmanda Purana, Uttarakhanda. But the Brahmanda Purana is divided into Padas, and not Khandas, and also none of the Padas have the title of Uttara-pada.
The scripture containing an Uttarakhanda is the Padma Purana, but this story doesn't seem to be in that as well.
So which scriptures talk about this story?