It's not so much exaggeration, but its more 'poetic' than just one-dimensional interpretation. Not just physical, but the spiritual interpretation of the character's actions.
The Amaterasu gate has no fighting power. It's basically a nullifying or an amplifying power. So it's not like she'll gain more ki or something. Like i said, i dont know wether its the translation or the author himself, but some of the sentences/phrases/statements have been grossely overexaggerated in Tenjou tenge(i.e saying Mitsuomi killed Shin, Bushinshi talking like Maya and mitsuomi had more then a platonic relationsihp when in fact they didn't even kiss, 100 yr War itself is exaggerated....) So It's kinda like a wait and see what happen game at the point.