Just to make note, nobody in the Maddox family is aware that Sai-Fung has magical powers, let alone that she's a deity. I haven't really thought out a power structure for that yet, but assuming that the mythological gods of old exist in the game (a logically sound element) then Sai would certainly be in that tier and she would be extremely powerful. Julius could put up a fight, so long as he's channeling Wanyudo, which again to elaborate is a small magic matrix about the size of a rubik's cube composed of painite gemstones. I haven't fully explained how that works, but I'll get to it.
Sai would likely see it as more strategic to conceal her powers until such a time that it's necessary to reveal them.