This is what used to get me so enraged in the week that the dowry episode was telecast. I just couldn't understand why the silly chits would go on living with abuse of any kind. There is no reason for it, esp. if the girls are educated and come from affluent families or have a support structure.
From what you tell me of your DIL, she certainly seems to have her backbone and brains both missing. If she thinks that this is going to give her child any secure future, she's simply deluding herself. But the biggest problem with such victims is that no one can help them, if they refuse to take help.
In slums and villages, when a man beats his wife, she kicks him right back and there's lovely free for all, with the wife beating the errant hubby through the back-alleys. maybe we should start sending some of our delicately nurtured damsels to the villages.