I was thinking that Jasmine would give you an item that allows you to catch Purior. Here's how it works.

You beat Jasmine. Jasmine tells you about Purior. You receive an item from Jasmine that helps you find Purior. The item will than (pick one of the choices below).

1. Allow you to find Purior as a wandering Pokemon.
2. Give you access to a new area that will have Purior waiting at the end. (like the Old Sea Map and Eon Ticket)

Having Jasmine just give you Purior is OK too, though.