Hi, Vincent —
The answer is, we don't know. It hasn't been defined. I believe the scales
tip in favor of her experiencing death. There is testimony from the early
church (though not necessarily trustworthy) that she died in the presence
of the Apostles, and when her grave was opened three days later, her body
was nowhere to be found.
The Eastern Church does celebrate her Dormition,
or falling asleep (=death).
Pius XII, when defining the Assumption, was
very careful to craft his words so as not to suggest one mode or the other. He simply said:
"At the end of her earthly life, she was assumed body and soul