Okay, so one of my theories has been ruled out as the prophecy pal; however… There’s some information here worth noting
Her bloodline is in some way connected to a forgotten god, (I think being descended from them would be a likely reason), which could possibly describe Tiamat. And if only the women are seers, then it would make sense for this god to be female; a goddess. She’s Japanese, so maybe not though. It’s far from impossible a descendant of Tiamat could’ve immigrated and/or been displaced to Japan a long time ago, though, so I won’t rule it out just yet. Maybe Tiamat is, in fact, the prophecy pal. I believe she could be both Eremis’ ancestor and the prophecy pal, or perhaps only one, but Tiamat is bound to be important in some way.