User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-85.154.148.148-20140118130924/@comment-1359322-20140119001110

Actually Rias did consider Yuuto as a candidate as one of the candidates to help break her engagement but due to Yuuto being a Knight that he is would refuse Rias' approach so Rias forgo Yuuto. Well Rias then chose Issei. In that point she hasn't thought that much about Issei until the training at the mountain. I guess the actual point is after Issei breaks the engagement.