As the goddesses with solar attributes are also associated with sovereignty,* this seems an odd change on his part. "Queenly Maiden" scans really well, though, so maybe poetic license also figured into it. One hopes. But it's not the only time Carmichael downgraded a goddess or spirit-woman this way. His collections of Gaelic prayers, songs, poetry and lore are invaluable, but between some sexism on his part and his atrocious handwriting, his translations always need to be checked.
*At least in Áine's case. We really know very little about Grian. We are not even sure she was seen as a goddess. The idea of her being a goddess or powerful spirit-woman (and not just the name of the sun itself) is largely based on her having a hill near Áine's, and there being folklore that describes them as sisters. Beyond that, there are parallels in the Scottish "two suns" idea, so some of this is reconstructed and supported by shared visions, and not necessarily written in stone, per se. For more on Midwinter in the Gaelic lands, Áine and Grian, and our other main Scottish winter festival, Hogmanay, see our Winter playlist: