Complex sentence: Orpheus Among the Christians, says that in "Sir Orfeo" Orpheus the hero is very Celticized, and says that the fate of Queen Heurodis is similar to the fates of other Celtic heroines.
Split into simpler sentences: Orpheus Among the Christians says that in "Sir Orfeo" Orpheus the hero is very Celticized. She cites the fate of Queen Heurodis and its commonality with the fates of other Celtic heroines.