@RtS That's actually correct, since 「ベルダンディー」 is the official version of Belldandy's name (Berudandi) in Japanese.
However, in this doujinshi they went for 「ヴェルダンディー」which basically sounds somewhat closer to Verthandi (Verudandi in here), who happens to be the original, Norse name for the middle Norn. Both names technically valid, since there's no way to literally translate Verthandi's name in Japanese, so the closest one can go is approximate it. In most cases she's called 「ベルダンディー」and even the official English name for her is Belldandy, reflecting this choice.
As far as I can remember, this may be the only doujinshi where they went for a different transliteration of her name. Which is kind of curious, although it's still pretty valid, and even closer to her Norse name.