No, I wont pass that judgment on Mala without knowing her reasons for leaving.
Many mothers give up their child for adoption or leave the child in the care of relatives if they feel they are unable to perform their duties as a mother.
Why is only Mala a bad parent? Dilsher did no justice to his role as a father. On the contrary he injected poison into a small child's mind and ruined his life for good.
In my books, both of them didn't prove to be stellar parents. Any absolution for Dilsher for staying back is negated by the ways he poisoned rudra.