what advice does her father give cassie regarding her relationship with lillian jean?

Papa basically tells Cassie to choose her battles wisely. Papa took her to the hollow with the cut-down trees. He told her that there were some things in life that you have to do to survive and that if she makes the wrong decision about Lillian Jean, Charlie Simms will get involved and there will be trouble.

Cassie don’t believe him much as to mama