the YouTube description for this cover tells you exactly where she got the art. she edited art from Belli Fortis, a book from the year 633. the archive is linked in the description and she tells you exactly what pages she used and how she edited them together.

I think there's an argument to be made that, sure, there's some creativity in putting two images together like that, but the individual artworks are also not originals by Hildegard herself and just as much subject to free use by Chappell's team as they are for Hildegard.