though she knew of her sons hatred, but that was way back, when he was only ten.
santu was also aware of the fact that megha had poisoned vishal's mind and personality.
but now she sees a different vishal, who is just talking every thing which makes her whole perception blurry...she doesn't have facts to support her past belief. i am sure if dm would have been put in the same situation , he wouldn't have believed any one with out a proof. dm over heard vishal himself, that is how he believed his true evilness.
santu will take no time to disown vishal, once she knows the true colours of vishal. she should trust her husband though....