Instead of anger I wanted to use word "frustration" but space kam tha😆
The point is that both Ishwari and Dev play with each other in a very subtle way.
Dev didn't let her know things like he used to often visit Sona during Natasha confusion track
He didn't let her know about their relationship
He loves Ishwari a lot but doesn't trust her to tell every details what he usually claims for
Remember waiting for 5 hours scene for Sona, that too was revealed for GKB to blame sona but Dev didn't tell Ishwari about it.
In case of Ishwari, mothers like her usually consider even opposite gender friends of her child as a threat so that they don't emotionally connect.
She knew since first time that Dev was responsible for Sona's termination where we're sanskaars at that time?
She had seen with her own eyes that during Devakshi's first dance sequence Dev pulled Sona for it(though we loved the dance) but what was the need to say that Bengali girls are fast when she saw it that from that angle Dev was super fast like Jet speed
Both of them do what they want but pretend that they are following each other and ultimately when they can't handle their own created complications they simply blame Sona.
Dev-humare rishte ki wajah se maa ka yeh haal hai
And Ishwari - Sona ke kehne mei aake dev ne mujhse ye sach chupaya.
I seriously want break up now
This is completely my point of view.