Honestly i just don't particular care about such vague prophecies...even more so if we get different tales from different sources.
These who have similar goals and loyal are welcome, the shemers who work against the MC will lose their heads, be it short or long term...
The thing is, the 3 snakes could be nearly everyone, neither we nor the MC knows much about the court, nobels, advisers etc. be it their characters, backgrounds or goals. I doubt one of the snakes is the mother thought, Alaina is far more likely with the reveals of the latest chapter, of course we could see next ep the mother sheming or a completely new character...or we maybe can replace a snake, like killing Cass and Isis taking her place, maybe we didn't even meet all 3 and so far the court seems full of shemers and snakes...i just find it kind of pointless to worry about the prophesy, didn't help the father much either...