My theory on Sibel is that the "goddess" mentioned might have been
Cybele - the view of her by the ancient Anatolians was probably different from how the Greeks portrayed her.
If that's the case, then it shows the fact that Turkey borrows a lot of its names from other languages - mostly Arabic and Persian, but sometimes other sources (the Turkish name Defne is indeed borrowed from the Greek
Daphne).
Sometimes names of pre-Christian/pre-Islamic deities are still used. For example, I heard the name Ninsun on a modern Assyrian
Christian. Ninsun was the name of a Mesopotamian goddess - she was the mother of
Gilgamesh. Names may be still considered part of a culture even after conversion to Christianity or Islam.