welcome to the forum and here's my bit..too
i have seen a neglected child and how it affects and damages them. I understand your pov and agree that it does happen.
radhika is unable to value dev's love because what she values the most is not available to her. a mother's unconditional love. she know she is not treated the same as her sister. she knows she needs to prove to her mother again and again and again that she will always do whatever makes her mother happy.
if you remember, the day vishaka and dev were to consummate their "marriage", she didnt protest, she didnt say the truth, she only hurt inside but kept mum. it was her mother's phone call that made her take action, because once again she was eager to pls her mom and do her bidding...
even when her mother had questioned why dev refused to take the pheras "again" with vishaka, she was quiet cos she was guilty as far as she was concerned in her mother's eyes
again she only went to tell dev the truth about their marriage when her mother told her too..