The key thing is that an apostle isn't a priest. So fas as we know, Paul wasn't a priest, either. His 1 Corintians 11 depicts the Eucharist as an already established ritual. Paul writes a lengthy description, complete except for one thing: who presides. There may not even have been a full-time status of "someone who regularly presides" in his churches. Maybe people took turns. Maybe everybody performed the ritual for themselves or their family. Paul just doesn't say.
Which I think brings us to this:
We know the sacrifice was performed from the beginning, so there was such a thing as a priest, if only for each time the sacrifice was actually being performed. We don't know whether or not its performance was a special office for the earliest Christians.
We know that there was always something special about the status of Apostle within the movement. It wasn't necessarily the status of being a full-time priest. Whatever the priestly office was, it wasn't necessarily confined to the Apostles and their pupils.
There isn't really a contradiction, then, between recognizing the Magdalene's unique stature within the earliest Christianity and yet not imputing priesthood to her.
As always, when I explain what I think a position is, it doesn't mean I agree with the position. On this particular matter, I don't have a vote anyway. It doesn't really matter what I think. For what it's worth, then, I think Mary from Magdala rocked. If I had to guess Jesus' intention, I'd have guessed he was down with Mary offering the sacrifice in his memory.
But I relaize I can't rigorously conclude that simply from her having other distinctions.