I’m going with an “orphan teenager fire victim” abducted by a minion of Ceto years ago, as she was laying her plans and plotting her and her children’s escape from Tartarus. (A nod to Wonder Woman saving her from a fire, but twisted.)
While encased in the mud and muck and stone of Tartarus, teen-aged Donna aged as she normally would, becoming a reflection of the young woman that the Amazons would eventually be tricked into creating with their Amazon Instant Pot or the cauldron or whatever that birthed the simulacrum Donna - the one that contained only a small “flicker” of Donna’s soul. (Explaining that horrible Titans Annual story, IIRC, that essentially said Donna Troy was soulless.)
So, the real Donna would have been abducted years ago, aging while encased in her clay tomb, and then partially/incompletely “resurrected” with only a tiny bit of her soul (the better and easier for Ceto to influence/control) by the Amazons via Ceto’s machinations during the Finches run.
Post this adventure, Donna stays with and joins the Amazons as a normal human woman. Some stories of her adventures amongst the Amazons follow, until the fateful day another Wonder adversary attacks Themyscira and in the course of that story Donna gains her Wonder powers, strengthening the bond between her and Diana more strongly.
Glad you enjoyed it, overall. Still some details on my part to figure out, but all in all a fun creative exercise to SAVE DONNA TROY.