I’m calculating the energy required to radiate that much heat, treating her body (or fist in this case) as a black body.

This is is the calc where she released it from her fist.

Fist area ≈ .054 m2

Temperature = 300,000,000°c or 300000273.15 K

The emissivity of human skin = .98


P = є σ T4 A

P: Radiate energy σ: The Stefan-Boltzmann Constant T: absolute temperature in Kelvin є: Emissivity of the material. A: Area of the emitting body

P = є σ T4 A = 24306230075928435759577996 W

24306230075928435759577996 W = 2.430623e+25 J/s (High 6-A) ———————

Now that’s how much heat she expels from her fist at that moment, but she stated that she could’ve evaporated the area if she released it from every cell in her body. In this case, I’m going to use the surface area of a human body for reference which is about 1.7 m2

If you plug in the same variables, but swap the surface area’s the result is

765196132019969273912640609 W = 7.65 e+26 J/s (High 6-A)

The first calc shows how much heat she released and the second one shows how much she could’ve released.