I am inclined to think she...probably could?
the terrasque is way above the Colchis dragon, it’s no push over, but raikou has decades of experience fighting oni and there are a lot of similarities between the two.
both generate mana or a related fighting power in their bodies, both corrupt the area just by standing in it, both rely on physical weapons such as fangs and claws
ik not saying they are exactly equal but her experience would serve her pretty well.