Not everybody who has met InuYasha for the first time thinks of him as a great powerful warrior, but rather just some annoying pest. Not only is this the first time Centra has met InuYasha, this is the first she's been in Japan. Centra is demon from as far away as Ireland. She flew to Japan because she wanted a far-eastern island where she could take a summer reprieve. She's always wearing a steel armored jacket with mesh sleeves and is armed with twin daggers because this is the middle ages and safe areas are not always a sure thing.

It just so happened Centra landed in Japan, when her scent was picked up by InuYasha. He perceived her as an enemy and engaged Tetsuaiga in front of her. She somewhat can understand him. At best, she can make small talk with someone in Japanese, but isn't completely fluent. She definitely can't read it. If someone, like Miroku, would pose a sutra to her, she will not be able to understand a word of it, therefore the spell would have no affect. But really there would be no need to cast something like that, since she has no ill-wills for Japan to begin with.