agreed wat Sneha did was wrong...but after all she is Prerna's daughter, and was showing the same behaviour as wat Prerna shows most of the time...Prerna has misunderstood Anurag, Bajaj, Prem, Sharad, Mukti and Jeevan, just to name a few...and not only that, she has even slapped Anurag and Bajaj, both of them being her husbands and elder to her...infact Bajaj might be around 20 years older to her and how dare she slap him?!
Well Sneha must have seen wat Prerna did to poor Kasak's life by disapproving Shravan at that time, and Kasak became pregnant before marriage(ditto Prerna)...so dont think she trusts her mom much, also considering the fact taht initially Prerna was also against Mukti and was not believing her, then suddenly she started believing her...and maybe she is also getting a feeling that Prerna loves Mukti more than her...
However, Prerna doesnt have the brains to explain the entire conversation she had with Sharad and how he had surrounded Mukti with 20 guys to gang rape her and the horrible dialogues he was telling Prerna...she is just going on saying 'main jaanti hu sharad ne kiya hain, mujhpe yakeen karo' and so on...