Ronova is OP if not bounded by rules.
Ronova cannot kill mortals easily, she follows the natural cause of death. The curse of death is one of the proof of it and mortals must resurrect again. She was also meticulous in protecting the mortals to deflect the attacks from the traveler. It shouldn’t be their cause of death considering it was indirectly caused by her.
She was too conscious as well to hide her true form to the mortals. Unless necessary, for example in the cataclysm.
She can fight traveler very well if there are no mortals around them, just like when Asmoday fights with the siblings, she went all out.