Her ways of communicating got a lot more... compact over the years.
The Celestial Comet
A Stone on some rope
When the relic was first made, it was but a simple rock tied around Ori's neck with some rope. The rock itself has a soft cyan hue, warm to the touch, with faint glowing embers sticking from it. But as years went by, the Fire Maiden improved upon its design.
A silver chain replaced the rope, and the stone got polished to a smooth level. Decorative silver encases the oval stone, whose embers remain lit within.
Link between Worlds
The Second Flame’s original purpose was to rekindle the First Flame, but that purpose was long fulfilled. Nowadays, Ori uses it as a method to communicate with Fasma.
When worn, it allows the Celestial to call her where needed. When directly held, it allows the Fire Maiden to gaze into the Celestial Realm and communicate with Fasma in person. The difference is that doing it this way is hazier than with the First Flame.