Ishwari has been shown as an iron-fisted mother who controls her kids' every movement, needs, desires, wants... all under the pretense of loving them and her and her only knowing the best for them. regardless of what age or how accomplished they are. her kids are brainless sheeps who follow her every command and are scared of her, more than love her.. i think.
Ishwari can not stand a smart, accomplished, thinking, educated woman to come and take over the household. do things that Ishwari couldn't do.. like the positive cultural related changes in Dev, like helping Dev make Nikki's growing up decisions, get Neha to xpt Ranveer's family's gifts etc. all this Ishwari couldn't do because she just RULED, instead of trying to understand her children's thought process and talking to them as adults.
Ishwari wants CONTROL and that she will lose if someone like Sona enters her household...