I googled the curtseying thing. It all makes absolute sense, in the 21st century 
As alluded to previously, the wife takes on her husband’s rank when the couple is together. In a sense, the husband’s presence validates the wife’s royal status. For example, if Meghan Markle and Prince Harry were in a room with the queen, Prince Charles, Camilla, Princess Anne, Princess Beatrice, and Princess Eugenie, Meghan would only need to curtsy to the queen, Prince Charles, and Camilla, because they are the only royals in the room who rank higher than her. In this example, Anne, Beatrice, and Eugenie would actually have to curtsy to Meghan because she takes on Harry’s rank, which is above that of those three women. (This would be the first time British royalty would curtsy for an American, according to Best Life.) Now imagine that same scenario, except Prince Harry isn’t there to accompany his wife. In that case, Meghan would have to curtsy to everyone in the room.
Sorry to introduce she who must not be named, it is purely coincidental 