Raimas friend had left the place and Raima as a good Samaritan wanted to reveal the true colours of Karan. We can laud her for it. At the same time she was a fool to think she can question and Karan would immediately confess.
Sona has been a kind soul that helps others without anything in return. She is too much of an idealist. Suman had realised her daughter was a celeb and capitalises in every way. Sona is the bread winner and any damage to her face will ruin her career and their survival can be a big issue...Suman warning Sona to not get involved is a very natural response.
Raimas mom had changed her name and was bent on keeping Karan away. Also when she knew Sona and Karan were friends she without thinking twice refused to meet her.
The same Tanushree Sengupta who had sought Sonas help now was rude to her....I a practical sense Sona and Suman are not responsible for Raimas condition is my POV.