User blog comment:B214/Question and Answers 6/@comment-73.57.25.92-20180811211147/@comment-10330822-20180813010843

Rias may know. She was just too self-conscious and that she was the problem.

Xenovia and Irina "might" know, however they still assist in Issei's "comforting" that ultimately allowed him to get over it. So its irrelevant either way.