I think she has done wrong to leave the home. What should she do now is that go that house and gave a good repky to Ishwari. She should tell her everything how every time dev and sona had to separate because if her. They had left on the roads, have to live away many years because if her pathetic behavior. She is a manipulative mother and the worst mother. Now she is trying to take kids away. If dev cones in support of his, give him a big slap. May be that will get his brain back.
Then finally threaten to divorce dev and take kids away. This is easy, sona is financially independent, kids need their mother, in court she can easily explain what all ishwari have done. She can get custody of kids that way.
Tell dev to leave his mom and come live in a separate house if he does not want to live away. If he does not that means he is spineless husband and father who is chosing wrong and his pathetic mother over them.