What does Taylor mean when she says, "all four of us have buried someone we love in Oklahoma"?

Estevan tries to explain to Taylor the metaphor of Oklahoma. He refers to how Turtle had seen her mother buried here, Esperanza finally begins to heal from the loss of Ismene (not exactly bury her) , and finally Estevan and Taylor will have said their goodbyes realizing they would have to forget about each other to move on to another chapter in their lives.