What might be the purpose?

She is truly extremely selfish and heartless naagin.

If she wanted to fram Bela so that will happen even if RJ is killed Bela was there only Kuhu will blame Bela only and due to Sumi's manipulation Mahir will blame her

So then why again Vikrant send Vish and gave her knife to kill baby.And Vish can kill that baby with her poison also so why there is need of that knife.

Baby won't be harmed in anyway we have got bts.

Whatever the reason is I will hope Mrinalji give proper reason for it.