CAW, as the name suggests Crime Against Women, but hardly they help the women. But in your case situation is entirely precarious. Herein, your brother in law and his parents have snatched the breastfeeding child of your sister, against her will, and expelled her from her Sasural, so she has taken shelter in Delhi at her brother's house (you). Is it so? However if that is the present situation, then she can file case in Delhi also. Please consult some good local lawyer.