Your right, death means seperation of body and soul. That never happened to Mary.
If you stubbornly hold that Mary certainly did not die then you are simply not a mature Catholic Memaw

.
A many have attempted to explain to you the question of her death has never been formally proclaimed either way by the Church. Please supply a clear quote from “Munificentissimus Deus” which has lead you to this strange personal view that it has? If we look at Tradition it is very, very clear where a formal definition would go if one had to be made:
Pope Adrian I: " “Venerable to us, O Lord, is the festivity of this day on which the holy Mother of God suffered temporal death, but still could not be kept down by the bonds of death…” (8th Century)
Pope Pius XII: "In the liturgical books…there are expressions that agree in testifying that, when the Virgin Mother of God passed from this earthly exile to heaven, what happened to her sacred body was…in keeping with the dignity of the Mother of the Word Incarnate…To cite an illustrious example … these words: “…the holy Mother of God suffered temporal death…”(MF 17).
Pope JPII: “Some … maintain that the Blessed Virgin did not die… However, this opinion was unknown until the 17th century, whereas a common tradition actually exists which sees Mary’s death as her entry into heavenly glory.”
And how do you know they her Body was lifeless???
MeMaw have you ever actually read the Encyclical (“Apostolic Constitution” to be exact) of Pius XII that defined the Dogma of the Assumption



?
Munificentissimus Deus states in black and white:
“The holy Fathers and the great Doctors…presented it more clearly. They offered more profound explanations of its meaning and nature, bringing out into sharper light the fact that this feast shows, not only that the dead body of the Blessed Virgin Mary remained incorrupt, but that she gained a triumph
out of death…”
If Pius XII says so when announcing the Dogma of the Assumption who are you and I to differ

So we wonder what exactly is the problem for you…
Can you really be so stubborn and unlistening that you will still not agree that both unbroken Tradition and the Popes have always taught that Mary died … simply because it has not been formally defined?
Or, as Jimmy well notes below, do you have to have it personally served to you as a formally defined Dogma before you accept it is the only unbroken Tradition of the Catholic Church since the First Century

?
Mary’s Death is not incompatible with the doctrine of the Assumption.
I think that is your real difficulty, perhaps you do not fully understand what the Assumption doctrine actually means

.
Yes Mary is alive and well in body and soul in heaven.
That does NOT mean she could not have died beforehand.
Clearly it is an unbroken Tradition since the year dot proclaimed by the Popes that she did die.
Yes, you may, at the moment, personally believe she did not die.
However you are quite mistaken to believe that:
(a) the Popes agree with you
(b) Mary never dying has been formally defined.
(c) Mary never dying is the traditional Catholic view
(d) Mary never dying was even widely opined before the 17th century.