Her MP is actually high. When she casts explosion she overcharges it so it uses all her MP. She could cast a few half-assed explosions if she wanted but that's not the correct way to walk on the path of explosions. Go big or go home.
Subjective feel of 'cool' however is a function of heat flux, not absloute temperature, i.e -10°C block of ice does not feel nearly as cool as flowing 1°C water.