User blog comment:B214/Volume 1 - 15 Discussion/@comment-50.172.213.125-20150109174032/@comment-120.164.40.190-20150109191548

@anon Well. it was to show Issei how bad the FA was ( they were still at war that time), if Rias just said to Issei that the FA is bad then chance is Issei wouldn't believe it, so why not let him feel it by experience. I believe Rias already researched about Issei's personality so she was sure that he would summon her.