I adore the anme
Demetria. While I like
Ceres in theory, it wouldn't be the easiest name to live with. But yes,
Demetria and
Ceres are a natural pair when placed side by side.
I would pronounce
Ceres as "SEER-eez." But from looking at the details, if it is based on the root "ker," I suppose it should be "KEER-eez" or "KEHR-eez." But good luck getting people to pronounce it that way. It would make a difficult name even more difficult to live with.
Did I tell you how much I love the name
Demetria? . . .