I dont think I can answer your question.
I think I understand what you are getting at, but with all the variations of wicca, and the ability for a single person in this religion to make thier OWN ideas and perceptions... there is no real concrete way for me to answer your question.
The answer i give will only apply to my perceptions and mean something in my views... for the next person it wont mean crap.
But.. in a general way, the goddess is an energy. Not a human who lived on the earth(like jesus), not an existing person (like Krishna), and not a person of power ( like cleopatra) .
In Wicca, there is an importance to recognizing 2 opposing energies, how ever you want to name them. There is a bit of science behind that as well wich I wont get into .. but.. an example :
It takes 2 to create one. If you want to create a stone, it takes sand and heat. If you want to create water it takes Hydrogen and Oxygen. If you want to grow a seed it takes soil and water... see what I am getting at? 2 elements combine to create one.
( people will argue that all they want.. )
God and Goddess ARE those opposing elements wrapped into one single word. They are the opposing factors of every element. They are life and death, air and water, sun and moon....
Does that help you understand what I am trying to say? Or did I confuse you?