I really don't believe Bloom gained the Vortex Flame from the test of the Vortex.
Many argue that she gained the Vortex Fire and it mixed with her Dragon Fire for two reasons.
1) She defeated the Fire Eaters, which requires the possession of the Vortex Flame, meaning that she must have it and it must have filled her empty space.
2) Her weakness was healed, implying the Vortex Fire filled her empty space.
I'm going to attempt to disprove these two theories below, as I believe the Vortex Fire didn't mix with her Dragon Fire.
1: disprove) If you look closely, at the time she emerges from the Vortex destroying a Fire Eater and when the last Fire Eater is destroyed in the hall, she has a magic aura around her: which I believe is the Vortex Fire. Meaning, her Flame Storm only destroyed those Fire Eaters because the Vortex Fire around her was still fresh because she just passed the test and emerged from the Vortex, which she used to destroy the Fire Eaters, so this disproves her actually having it in her.
2: disprove) I believe she regained her strength because the spark of the flame she gave herself reignited in her, just as the sparks in the Winx ignited when they gained their Bloomix, filling the empty space where their powers once were. She was healed because her spark ignited in earning Bloomix, therefore filling the empty space within her like the rest of the Winx did with their magical energy, not the Vortex Fire.
This has been on my mind for a while, because the two fires mixing didn't seem right to me. Let me know what you think!