That is true that like in England the new monarch is crowned a year later, but that doesn’t mean that they aren’t queen immediately. Snow is queen no matter what immediately. Unless they just have that Regina took over through power, Snow let her,Regina tries to kill her, Snow runs, Regina accuses Snow of murdering her father and being a traitor, so everyone turns on Snow for awhile. They need to show why everyone thinks that Snow is a traitor and a murderer.