Range increases by 2 units (4 units overall). Stacks additively with Heat Sense. Does not affect Fire Sword, Flame Thrower (without Heat Ray), or Elemental Transform's swiping attack.
5
Unlocks Heat Ray.
6
Fireball pierce increases by 2. Has no effect after upgrading to Bigger Blaze, which always sets the pierce to 8.
7
Unlocks Elemental Transform.
8
Range increases by 2 units (6 units overall). Stacks additively with Heat Sense. Does not affect Fire Sword, Flame Thrower (without Heat Ray), or Elemental Transform's swiping attack.
9
Fireball attack cooldown reduces by 0.2 seconds, increasing its overall attack speed by ~36%.
10
Fireball attack now shoots two fireballs at a time instead of one, spread 45° apart from each other. Does not apply to Elemental Transform's version of the attack.
Flame Princess is a decent damage dealer with a significant power spike at 10 stars, effectively doubling her DPS output, however before that point she can be considered weak and restrictive compared to other options. Her ability sadly does not receive the same buff at 10 stars making her a lot weaker when it is active.
Build to avoid Pierce buffs to ensure Fireburst can activate, making Wand of Dispersement the most optimal choice over Cherry Blossom Wand. Speed and damage trinkets as usual are good. Wizard Nunchuks may be considered to stop DDTs if one is having trouble with them.
Outside of damage, she is the best character to tag MOABs with Thought Cannon Wand, though this significantly weakens her damage output and one may opt to run her more as a support build at that point.