Well, this is interesting.
I wasn’t taught anything one way or the other concerning this issue. Perhaps I can share a few thoughts?
I think it was one of the Cappadocians who discussed Genesis where it says ‘dying ye shall die’ - his thought was that the original plan was for man, eventually, to return to the dust and rise again, but it would be a death without fear or corruption, lest the world be overpopulated. It would not be a death to the death, that is a death to corruption, but a death to life, to a resurrection. It would not have been a death because of sin, but a death because of the promise of new, eternal life. I’m sorry I can’t place the quote.
We don’t know exactly what happened, for sure, it seems, although different things have been taught from before anyone who is alive today remembers.
But IF Mary died, it would have been as the new Eve, no? As a model of Christian death, a death unto life, not a death unto death? A death without sin and without corruption, and a pure and holy resurrection? IF Mary was sinless, THEN she would not have suffered a death of sin, as death is the consequence of sin, but a death of redemption, in which the marks of the world are swept away that happen to a person even living sinlessly in the world.