The Supreme Goddess Is The Mother of the Universe, almost identical with the Brahman of Vedanta, but only at the transcendental level. No doubt The Goddess IS The Supreme Self, but She IS Also The Collective Self.
At the relative and phenomenal level, where there is awareness of one’s own individual personality or ego, even Her Manifestations follow the same law, the same order that is seen in the rest of the universe. The Various Emanations of The Goddess Combine both the Transcendental and Phenomenal levels of truth to varying degrees. It may not be inappropriate to suggest that while ultimately at the transcendental level She Is The Supreme Self or Brahman, In Her Manifestations As Other Goddesses She Is Also The Transcendental In The Phenomenal. In other words She IS The Transcendental, She IS the Phenomenal and She IS also The Transcendental in the Phenomenal. This is the uniqueness of the Shakta world-view.
Reference: The Glory of the Goddess-Devi Mahatmyam, Dr. Satya Prakash Choudhary