Maybe...but i just think they're many dimensions where everything is happening
spoiler
.
.
.
.
.
.
.
as far as I can remember you are correct, the OG irene is now living happily in the modern world, and her boy friend is the fake saintess crush, the number 1 hunter in korea LOL
OMG, FOR REAL?! ÔoÔ
Honestly that would be an awesome setup! Not only to say "In your face, Seoyun!", but because that way both girls would have gotten what they wished for. I mean, this was only my interpretation, but if Seohyon's wish was to have a loving family, I imagine that Irene's might have been to be healthy and strong, since she suffered through a sickly childhood and eventually died of it T_T.
But since the story regressed in time, and all this is happening BEFORE Ciel went to Korea... might Seohyon still exist and be alive in the real world, while her Irene soul is in-world?!
Or who knows, maybe the actual Irene's soul also transmigrated and is inhabiting Seohyon's body, as if they switched when she died as a young girl.