At the time this was posted on Pixiv in mid-2013, BeelStarmon wasn't official yet (Watanabe Kenji, "the chief designer for Digimon" (quote from Wikimon) and her creator, provisionally named her "Beelzebumon Lady" or "Beelko" before she was finally named Beelstarmon [those two former names ended up being used in her lore]) and he was "waiting for official approval".
At least based on machine translation of the commentary above.