i think one big question we need to ask ourselves here is, who cares? Even if the information the game gives is ambiguous enough to justify that kreia is handmaiden's daughter, the fact is that it doesn't affect the story. The only relationship between the handmaiden and kreia that exists in the game is that handmaiden is used so that kreia can reach the Telos academy whenever she wants. And the only other thing is resentment for any feelings the exile might have for handmaiden because she thinks it will weaken him.
The dev's give neither any indication that kreia is her mother, nor does any of the dialogue in the game. This whole thing is based on a "but they dont say she's not" argument, but they don't have to, Kreia doesn't like handmaiden, and as atton says, the only reason she had her onboard is as a pawn. Not only that, but she didn't fight in the Mandalorian Wars, unlike handmaiden's mother, as kreia was only exiled from the jedi AFTER the mandalorian wars, as indicated by the holorecording of exile's trial.