Filvis Challia

Would someone slowly explain this all to me?

How is it possible for Filvis to be Ein too while they are in same place, same time? I just finished SO volume 11 and to be honest I not get it at all... I could imagine her changing to Ein wile noone is around but... on the epilogue we see them both face to face! Same go with Dionysus-Enyo killed by himself...

I thought both are dead once for all so after I finished volume so I came here to take a peep if I missed something about them.. and now I'm confused as hell...

Honestly, when Philvis died in the 11th volume of the oratorio, I thought that the author plans to make friends with Lefia by one of the xenos in the 12th volume. But in the 12th volume we will see Philvis again.

Now that she is dead as a monster. Can we expect her to be reborn as xenos? If so, what type do you expect? (presumably, harpy, wyvern, siren, etc.) due to the friendship of Lefia and Philvis. I am also confused by this picture at the end of the volume. Where are the zeroed parameters of Filvis.

Or do you think that Philvis is finally dead and will not happen again?