Ashey said: Since the very beginning. Following the canon, she already became youkai-magican, while Marisa is still human. That means the potential magical power, that Patchouli could accumulate and use is the way, way higher than Marisa's. Any questions?
In canon she's a "Witch" (People who are born with magic) while Marisa is a magician (people who learn it through study). She never "became" youkai.
It was never clear if witches are better than magicians. But it doesn't matter - Marisa won against Patche two times in spellcard battles.
Also this is a DREAM (well more a NIGHTMARE). Hence the heavier outlines on the panels. It takes a little time to get used to noticing what is a recollection of dream/hallucination for Marisa in this
Do you understand...? I used your spell, but...Its firepower changes this much when a real magician uses it... Your firepower is that low......If you still don't understand, I can hit you next time.