This article's content is accurate to the most recent public game version, 0.4.8d.
"[5 Turns] Grants immunity to Fire, +25% ATK and attacks gain Fire attribute. Removes Chilling Aura."
Cost: 5 MP
Source: Equipping the Shadow Core.
Flaming Aura is a spell that applies a buff that makes the user's default attacks and grants immunity to the 
Fire element along with +25% ATK (Not the same as a standard STAT Up) for five turns to the user. It will also remove the buff granted by Chilling Aura if it is active.
This skill is best used in prolonged fights by a physical attacker such as Veronica (or anyone else with an ATK build) to buff their primary means of doing damage. However, it can be used solely for the immunity to Fire, should you need it.