Maybe the "mystical clone" origin needed a little cleaning up but I thought it was more interesting. Personally if I was rewriting it I'd change it so that as an early manifestation of Diana's powers that she accidentally created a sentient imaginary friend named Donna. As Diana grows up beyond the need for an imaginary friend Donna who still lacks physical from fades away into limbo. It's there that the Titans of Myth discover her, and give her physical form as one of their Titan Seeds, or maybe as a new twist they use her soul to create Devastation.
That could also just be the new Devastation origin, and Donna could just be a human girl like a lot of people seem to want her to be. My idea doesn't really fit in with the current continuity anyways since Diana didn't grow up as the only child on the island, and thus wouldn't have had such a strong need to create an imaginary friend.
Either way her absence could be attributed to being with the Titans although the idea of her being a trans woman who was living with that male amazons does sound interesting too.