The Universal Mother whom countless yogis have come in contact with and found the royal path to liberation from the bonds of fear and ignorance, She is everywhere and in everything. She is One and yet manifests on all planes of creation from the gracious Tripurasundari of the Dashmahavidyas and Siddhidatri of the Kundalini to the lowest planes as Dhoomavati and Kali. All creation is Her endless act and Her infinite Glory can never be captured by any scripture and stuti. Beyond Her universal aspect, She is the Parameswari, the supreme Shakti of the Parameswara, the supreme Divine Nature or the Paraprakriti of the Gita. Yet, though Transcendent and Supreme, though Universal as the World Mother, from time to time She incarnates some portion or degree of Her Force to carry on the evolutionary journey of the earth, lokasangraharth as the Gita says. These are many earthly embodiments and incarnations whose names continue to inspire mankind. Savitri, Sita, Draupadi, Radha are some of them. Or to use the more recent ones, we have Anandamayi Maa, Sharada Maa, or even heroic personalities embodying Her Kali aspect as Jhansi ki Rani, Durgavati, or as reformists and queens empress who changed the world in better ways such as Catherine the great of Russia, Hatshepsut of Egypt, Ahilyabai of the Maratha empire and such others. These incarnations take place when a certain specific work is to be done upon earth which cannot be done otherwise. This is so because while the Transcendent and Universal Mother are omnipotent, yet one needs an earthly body and being to hold this Force and direct this tremendous Power for the intended work. Therefore, She who is beyond, the ultimate Secret Wisdom and Might assumes a human body from time to time for a specific work.
It is thus and with this background that one has to see the birth and work of Mother Mirra, who is generally referred to as the Mother of Sri Aurobindo Ashram. She too is a descent or an incarnation of the Supreme Mother who came charged with the mandate of transforming earthly life through the Supramental manifestation. This earthly mission was specific to this form of HER so to say and hence it is through Her that this will be accomplished and is on the way to its fulfilment. There is no contradiction here with regard to the other forms of Her manifestation, each of which had a particular purpose that could be fulfilled only through that embodiment. Otherwise, Her advent (as also the advent of the Ishwara as the Avatar) would be meaningless. It is this mystery of the incarnation, the Avatar, that is so beautiful and unique to Sanatana Dharma since it allows for the evolutionary progression of the Divine unfolding in Creation itself, the Lila. Rama and Krishna are the same and yet there is a difference in the work they came to do, the Age and the type of humanity they were addressing and the aspects of the Divine they manifested. So too Shiva and Vishnu are the same yet they represent different aspects of the One Infinite. The beauty of Sanatana Dharma is that it does not forget the uniqueness of each element of creation even when always remembering the essential unity. It knows that God dwells in all and yet knows the distinction between the workings of God in Duryodhana and in Arjuna. It knows that the Divine though forever the Same Immutable Lord yet moves ever forwards in His Manifested worlds through Vibhutis and Avatars. Mother Mirra, understood in this sense is the Avatar of the Divine Mother who has come with the mission and the mandate of earthly transformation. So if that is what one aspires for then it is through surrender to her (as an embodiment of the Divine Mother entrusted with a particular work) that one undertakes the yoga journey. But if one seeks liberation or any other worldly and other worldly boons then there are several other aspects who can grant this if one knows how to truly surrender.