As it is very cleared it is Adi as most of us guessed now I think even the lawyer and all is Ishita's plan to know what is the real reason of Raman's silence.
As knowing Ishita's character she would have not done the case if Raman is havng any problem because she was ready to take the case back for Simmi so she can definitely do it for her husband, but her only anger is that Raman hid it from her which is genuine.
And coming to the lift scene where she will say Shagun to ask forgiveness and she will forgive her and withdraw the case [as per spoiler] that is because Ishita wants to know what is Shagun upto because knowing how selfish Shagun is she would have never left this chance and would have agreed to Ishita and also if Ishita's motive was to make her ask for forgiveness she would have said the same to Raman and he would have made Shagun ask for forgiveness.
And now seeing Shagun adamant she may think that there is lot more to what she knows.
As from the very beginning Raman was shouting MAJBOORI MAJBOORI🥱😆 and even when he isn't in his full sense he said Ishita doesn't know the whole truth
So I think ishita has something cooking up in her mind or else who calls a lawyer on their house when the husband is laying on the floor all drunk😆