I'm afraid this is going to be immensely unhelpful, because I don't remember title or author - but maybe someone else knows the book. But I *have* to mention it, because it is in fact a children /ya book about *the* mother goddess set in the Stone Age (altough possible German).

http://de.wikipedia.org/wiki/Venusfigurinen

(the links in German, but it's about the pictures...)

It's the story of a girl who is in the course of the book, becoming a shaman/priest of the mother godess. There's dreams and visions, if I recall correctly. In the end she is making (carving? sculpting?) a figur of the godess...

There. (And I know I'll spend more time looking for the title.)