So... Merlwyb will be voiced

[Alhanelem]

English, Japanese, German, or French...Doesn't matter. I doubt any language is capable of capturing Merlwyb's personality.

I don't think you or any of us really understands her personality in the first place. It can only be defined with how she speaks in each language, together with the actual dialog. Her personality is going to vary slightly in each language, tehre isn't much avoiding that.