Hmmm, I would think from a purely intuitive point of view that a wand with a spell bound to it casts the spell, but then that goes back to a previous question of when using an item with magical properties, who is acutally causing the magic?
Example: Staff of the Beasts, are the effects a spell stored in the staff or a spell cast by the beastmaster through the staff?
If I were DMing this, I would say no dice for the priestess as the wand has the spell stored in it and she is just activating the wand.
Does anyone have any clearly worded rules that answer this?