Social Security Child's Benefits?

My daughter recently got cut off social security child;s benefits which she was drawing off her father who is still getting social security disability benefits. I want to know can they cut her benefits off because of an overpayment? I thought that if he was still receiving benefits than she would too and also I thought that she would receive benefits no matter what until the age of 18. Can someone help me please. Also do I need to consider a lawyer?