User blog comment:Ixarising/High School DxD Dream Battle/@comment-112.211.199.137-20140207162046/@comment-1359322-20140207164754

I'm taking his definition of "Evil" for Issei which is "he lusts for power and nothing else. He would prefer to kill and use his full power, no holding back. Opposite of how Issei really is."

Thus based on the scenario given, i've concluded that Rias won't spent even one of her Evil Piece on this Issei.