After all a mother is a mother. You will always feel a bond with her. Plus Nirmala does care for Shaurya, she may be a bad person and the relationship she shares with her son is tense but still both of them have acknowledged their bond. Remember the engagement time when the truth comes out, Shaurya accepts that Nirmala is wrong but still talks about his acceptance of her. In their talk in the club again he talks about the difference in the ideologies but never says that he hates her, does he?
So I still believe he is innocent. On the other hand, Nitya after her initial acknowledgement of being the killer is taking too much interest in this matter. And her insistence to Anjali about Shaurya being the killer is a little over the top. Hope Anjali has some common sense to take an impartial road. She does have people like Shlok and Disha to help her so why doesn't ahe ask help from them.