In original Greek, the Ph sound was an aspirated P, not an F. The closest approximate in modern English would be the "p-p-p-p-poker" in the song Poker Face.The AE diphthong is pronounced AY as in eye.Thus, to be perfectly historically correct, Phaenna would be Pie-nah.However, names change with movement into other languages, for example, Pear-iss, not Pah-ree, in English (Paris). Therefore, Phaenna could legitimately and with historical precedent be pronounced variously, Fee-nah, Peh-nah, Fay-na, or Fie-na, and no one could really correct you.
― Anonymous User 3/20/2017
6
I would pronounce it "fah-enna," but I have no idea.