If you already have one of the items needed for the quest in your possession when you reach a step, you can force the quest to continue by selling an item to a vendor and then buying it back. Conveniently, there is a vendor Sage Elrendir located just inside the hut next to Elowys. Trading the item back and forth with another player will also give you an update.
You must return to Elowys to complete each step of the quest. You can't collect all 3 butterflies and submit them at once. If you do collect (or buy) all butterflies at the same time, you need to use the vendor trick mentioned above to have get the update.