Radhastami is this Wednesday so I've been reading about and meditating on Srimati Radharani.
In Srila Jiva Gosvami's commentary on Sri Brahma-samhita, verse 3,there is an interesting section talking about Durga and Radha:
"Sometimes Goddess Durga is also described as the supreme controller. This is also correct because there is no difference between the potencies and Lord Krishna, the master of the potencies. This is confirmed by the following words of the Gautamiya Tantra:
'Krishna is Durga. Durga is Krishna. One who sees that They are different will not become liberated from the cycle of repeated birth and death.'
Durga is the personal potency of Lord Krishna, and therefore She is Lord Krishna Himself. For this reason Durga should not be considered manifested from a portion of the Lord's illusory potency, Maya. This fact is confirmed by the following statement of the Nirukti:
'Even if one continually worships Her, Durga is still difficult to understand.'
Durga is also described in Narada-pancaratra, in the following conversation of Sruti and Vidya:
' Durga is the supreme goddess. She is an incarnation of the Supreme Personality of Godhead. She is the transcendental potency of the Lord. She is manifested from the form of Lord Maha-Vishnu.
' Simply by understanding Her one immediately attains the Supreme Personality of Godhead. It is not otherwise.
' She is identical with Gokul's queen Sri Radha, who possesses a great treasure of love for Krishna. By Her grace, the Supreme Personality of Godhead, the master of all living entities, is easily understood.
' She is the potency of personified devotional service. She worships Her beloved Supreme Lord. Because She is understood only with great difficulty, the saintly devotees call Her Durga, (difficult to understand.) She is the personal potency of the Supreme Personality of Godhead and She is always filled with the nectar of love for Him.
' From Her is manifested the mah-maya potency, the controller of all conditioned souls, who covers them with illusion. By this maha-maya potency the residents of the entire world are bewildered into thinking themselves identical with their external material bodies."
In the Sammohana Tantra, Durga Herself declares:
'I am Durga. I possess all virtues. I am not different from Sri Radha, the eternal, supreme goddess of fortune.'"