My guess would be maybe true soul Gut, since we know she is infected.
Nay, origin means one can play as it, so it has to originate from the ship. As other pointed out Helia is the main suspect - she has been datamined in early patches, though as Larian got more thorough with what they ship with each path, we haven't heard of her in a while. We are still very short on good origins, so I hope the new origin will stand aside Karlach as a potential good aligned party candidate.
You know what else was datamined early? Warforged, Aasimar, Tritons, Genasi, Lizardfolk, etc..., so datamined early doesn't mean shit. Warforged even had a voice line.
On the other hand we actually see Alfira in the Baldur's Gate clip looking like a PC.
