What about Patty and her parents in The Summer of My German Soldier? Why does she lie about the P.O.W's?

Patty Bergen is a troubled teen, friendless, set apart by her nationality, and put down by her parents.  Her mother and father have serious issues of their own, and constantly criticize her and tell her she is no good.  As is so often the case in dysfunctional homes, Patti responds by exacerbating her own situation, lying, exaggerating, and and generally perpetuating a cycle of bad behavior on her part and resulting parental disapproval.  In addition, the boundaries between fantasy and reality become blurred in her own mind, further contributing to her difficulties.

Aside from an arguable element of sheer orneriness, Patti's behavior in lying about the arrival of the POWs in Chapter 1 stems from a desperate desire for attention.  Engrossed in his paper, her father is annoyed that she wants to talk to him.  When she finally does get him to listen to her, she feels "like an actress who finally gets her big chance", and embellishes her tale in hopes of leaving an impression, as well as to make herself feel important.  Characteristically, her father hears her with disinterest, abruptly dismissing her when she is done with the comment, "let me read my paper in peace", giving the reader a sad insight into why Patti might act the way she does.