Q: What is the Virgin Mary? Is she a saint? An avatar? Divine Mother of some sort? What is the difference between her and the mothers of other avatars?
I can only reply to your question according to my own study and my personal experience. So it is all only my opinion.
I believe that the Virgin Mary is a siddha-purusha, one who has scaled the entire ladder of evolution and attained the ultimate realization, and is therefore a perfect reflection-manifestation of the Mother aspect of God. In my book Robe of Light you will find more about her history and relation to humanity in general.
The other mothers of avatars surely were of a high spiritual development, but there is no indication in the histories that they were as exalted as the Virgin Mary.
Further Reading:
- Discover The Unknown Lives of Jesus and Mary
- Questions on Cosmology, Evolution, and Avatars
- Divine Incarnation: Which is Your View of Avatars?