I don’t really understand why Snow isn’t Queen already. Her father died and she is the heir. The throne should have gone from her father to her and had nothing to do with Regina. Regina would just be like the Queen mother though she isn’t Snow’s mother so i am not sure exactly how that works, but she is not the one of royal blood so the throne wouldn’t go to her. Though this is fairytale land so maybe power wins that game instead of succession by blood.