Posted:
Means known from past SUBBU is very desperate about kids and when he is expecting another one from her and she can't provide him one.
May be he was torturing her and she felt indifference towards her.
Then Toshiji might have motivated her to fight against injustice and leave him with kid.
Then in attempt of leaving Subbu might have accidentally killed them.
He might have hide this fact from her mother.She is thinking Toshiji might be reason for their death.
Technically this reason is enough for any psycho to tend towards revenge.