probably something like that.
i'd bet that was what they intended that scene to be, but since everyone only knew of her explosive black arrows, we all took it as that. now with the context of the last cinematic, we can know "well shit, this is why she thought she could fight malfurion". seems it doesn't one shot malfurion though, or his life magic counters it enough to keep it from killing him outright.
we see in game that he's still winning the fight though, even with her new powers. so she's amped all to hell, but still not quite malfurion level.