That is a good question, and one
that was never answered by the Church.
In fact, when Pope Pius XII defined
the infallible teaching of the Assumption he used the language
"When her earthly journey
was complete . . . "
We may believe either way.
- There are some fathers of the Church
that believed she did die right before
being assumed into Heaven, which
would mean there was no bodily decay.
- Other fathers claimed she didn't
die, but rather it was more of a
deep sleep or dormition, similar
to what happened with Adam, when
Eve was created from his side.