Did you see Opaline’s face at 03.15 in the episode? It was as if she recognized someone and was horrified by this. She then becomes enraged, and the green light around her indicates strong envy, so it is possible that she knows what it was she saw. It wasn’t just the magic, though she was honest when she declared it should be hers, this ran deeper. It is clear that she did not know beforehand about the Wishing Star and its mysterious connection with the Unity Crystals.
At least we know that the dragon fire is necessary to awaken her alicorn powers. Which had been sealed after Twilight defeated her (possibly along with the Mane 6 as suggested by IDW) and took away her magic. As the magic was released, Opaline was supposed to regain her magic - but her alicorn powers were sealed away. That is why Opaline needs powerful magic to break this seal.
Twilight knows her stuff, it must be said. There are many indications that Opaline did not have an important role when Equestria collapsed and the active magic was sealed, this can be proven in 03.15, which shows that she was not familiar with the matter surrounding the Wishing Star. When she saw the star, the Mane 5 and the Unity Crystals unite their magic - it was such a shock that she was completely shaken and then completely mad with rage. She recognized something! Was it the magic or something else?…