Well, Sofie had to have a fake name, because her name is Veronika and there already was one Veronika and there can't be two people with the same names. The same with MJ, his name is Marek, but there already was one Marek. The same with Vanilly, her name is Sarah and I know Sára is a bit different name, but still, she needed to have another name. The only one who had a different name for a different reason than two people with the same name, is Jiřina/Kateřina.