The beautiful friendship destroyed when Grezia's powers started to show up when she got to fifteen years. They were so sudden, so strong and powerful, that everyone was shocked. Her peers were trying to bully her, and Zirta defended her. So the bullies turned their insults to Zirta instead. That's what acted as trigger for Grezia. They could bully her but not her friend. Her powers surged out of nowhere. They were so strong and powerful that Zirta's powers were instantlt put to shame.
It wasn't long before everyone started to admired and praise Grezia and that caused jealousy to bloom in Zirta's heart. Grezia was becoming more powerful and idolised. She relied on Zirta to help her train as she didn't like the attention which she found hypocrites. She confided into Zirta to help her be less overwhelmed and train.