n she just asked shivam tht he shd have confided in her , tell her about Riya..her frustration was jaayaz as she was completely clueless yet nobody believed her ..she felt let down by shivam n here it was shivam's mistake too..
Her frustration was valid. But I don't think it was Shivam's mistake either. Shivam himself wasn't clear about his feelings for RIya. Had this wedding fiasco not happened, he wouldn't have proclaimed his love for her so soon. Since he had to figure this confusion out in a matter of a day or a few hrs, there was no time to tell anyone.
Kausalya gets blamed whether she knows things or she doesn't. In such a situation it would be best that she doesn't. Even if she knew anything, her claims of having begged Shanti and Raghav for Shivam and RIya's rishta, would never happen. SHe would try but would have been shut up immediately by the mommy/son pair.