Meaning of Hannah's last appearance

Question

In the last episode of season 7, we see Hannah McKay leaving a black flower at Dexter's door.

What does it mean?

Will she try to kill him or was it a goodbye-gift meant to symbolize her sadness that he betrayed her? Or is it something else?

Answer 1

From the executive producer (Scott Buck) :

Buck: It was a very dark shot, but it was a black orchid, which is meant to be a very ominous sign from Hannah that Dexter would understand what it meant.