Why does Mrs. Morrill wish Greta "safe passage"?

Mrs. Morrill wishes Greta safe passage because Greta is beginning a journey that will last the remainder of her life. Greta's father echoes Mrs. Morrill's words when he tells Greta that even though she thinks she has lost the world she is leaving behind in Blue Cove, she will always hold the memories of her time there close to her.