Child Support( ex mother in law freaking out)?

My wife has to go to court the other day because of her ex husband not paying child support. HIs mother pays his bills for him and enables him to be a dead beat dad. His mother was in the court room and confronted my wfe by throwing receites in her face from her buying clothes occasionally for the kids. It is me who takes care of the children, not him or her. I pay for it all. She buys clothes sometimes for the kids, maybe 2 times out of the year but she cornered my wife at the court house and told her she needed to repay her for buying the kids clothes from time to time. We left the court house without saying a word to her . Then she shows up at our door and tells my wife she wants money for everything she has done for her grandkids. She is mad because the government took her son to court for non payment of child support, not my wife. Should we just ignore her? Her son owes alot of back child support and refuses to work. In fact, he works for about 2 weeks and quits.