How does the author use foreshadowing in Harvey?

Act II, Scene I is also important because of Veta's speech about art. During this
speech, her character gets to the very heart of the play. She says: "A painting shows not only the reality but the dream behind it – It's out dreams that keep us going. That separate us from the beasts." Harvey is Elwood's dream, and it is because Veta makes this speech that the ending of the play is foreshadowed..... will she allow his dream to be taken?