Yeh.
When you do read my fanfic you will notice I even explain in my own way, but through Prue mostly how the Source got half a face if you remember him.
Prue from the time period I normally base my fanfic around burned half of his face as that was only going to be the way she could escape from where she was in underworld after being captured by demons. So the Source could try and kill her sisters first when they came looking for her. She even had a talk with the Source, but as you know the Halliwell's don't like talking with Evil very nicely, but will listen to Evil.
Prue burned the Source to where he was weakened by her inferno of fire and she also burned the demons that were going to take her to the Source the 2nd time around, but she vanquished them and then went after the Source.
Prue would only use that much fire if she really had to as it can weaken her too by using that much energy of her dragon witch side as all dragons and dragon witches have their limit for how much fire and ice they can use. The same energy is used to help her fly, but in the underworld she is unable to do that.