Pressure toh abhi bhi hai. And when he knows about pregnancy, he would know that it ain't his baby and that Rhea cheated. He won't agree to marry. And even Daadi would have her doubts on Rhea's character, considering Daadi's mentality.
The nice girl pretence would go as soon as the truth is out.
Here is my prediction,
Dadi-Rhea planning till the end to break Ishqaan wedding and get Rheaan married. When everything fails, Rhea goes to Ishqi and tells she is pregnant with Ahaan's kid. Dadi still doesn't know. Ishqi goes missing just because she is disturbed and needs time alone. Dadi-Sarla makes scene and asks Ahaan to mary Rhea. Dadi threaten/blackmail that if Ishqi doesn't come Ahaan has to marry Rhea. Ahaan trusts that Ishwi will come back on time. Dadi makes Rhea wear lehenga as they are sure Ishqi wont come back. But AVM is still sure that Ishqi will be back. And Ishqi at the end trusts AVM and reaches mandap. Rhea's mom will lose and blame Ahaan in front of everyone for pregnancy. Ahaan and everyone are shocked. Ishqi will shut them up and get married to Ahaan. Dadi is shocked with Rhea and now agrees reluctantly for Ishqaan wedding as she cant do anything.