This is basically Lisa/Risa fued all over again. So I'll explain it here so I can save Halo some typing.
So for no complains, I'm going to call Lilie/Lily "Riri"
We all know that the official merchandise spells Riri as "Lily", but the reason why the admins have decided to call Riri "Lilie" instead of "Lily" is because "Lilie" is something that suits Riri's personality and character in general better.
Our second argument would be that "Lilie" is an alternative form of "Lily", and is the exact same thing only with different spellings.