User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-104.7.80.176-20150603035954/@comment-16281343-20150603072435

The hell are you saying?

First, they know nothing about Issei and what Raynare was planning. Issei being given a leaflet was a matter of chance. Issei even had the chance to throw it away but opt to not.

Second, Rias being summoned by Issei is also a matter of chance. Issei wished strongly for Rias; that's why she was summoned instead of the other servants.

Third, no one knew that Riser would push the engagement up. Rias and her family had an agreement that that event would be postponed up until she graduates college.

TL;DR: Rias didn't plan anything. Rias didn't know anything.