I suspect that one source of the confusion is that The Eldest was described as being Asian in appearance, and Soraya as having a connection with Japan. But there is no direct relationship between the two.
Soraya is the head of the Blue&blacks, and claims to be perhaps 8000 years old. The Eldest is much, much older; it is said that she dates back to the dawn of speech. That would be 50 – 100 thousand years ago. Soraya works closely with Alexandros. The Eldest is a power unto herself. — Stephen