The ending - did she do it?

That's kinda what it seems to be to me.

On the basis of the evidence presented at the court trial, the jury had no option but to find Kya not guilty, because of the lack of formal evidence showing she had means & opportunity in order to do this, in spite of the strong motive where she had been heard threatening to kill Chase.

But even accepting that she returned to Barkley Cove from Greenville, and returned there early the next morning, how could she have been with Chase at the top of a fire tower in the middle of the night, pushing him through the opening?

The damning evidence is of course the discovery by Tate after she had passed away, of the actual physical necklace, that it was known Chase had been wearing that evening. If the jury had been made aware she was in possession of this necklace, that most certainly would have convicted her.

Yes and it was always obviously that she did it.

One of the most predictable movies I've ever seen.

You were supposed to be able to assume that... but it would have been much more plausible if the black guy at the store had done it since he asked her to tell him when she was going to be out of town, that would give him the chance to kill him and be sure she had an alibi. So it was more likely that he killed him. Was also equally possible that he had left the necklace at her house when he trashed it just to make sure she knew he was the one that fucked up her house. The mother in the trial had simply said that he always wore it but she wouldn't have known if he had it on that day or night or had left it at her house as she wasn't even aware of what he had been up to nor did he wear it on the outside of his clothes. Unless mom had been watching her son without a shirt on she wouldn't have known anything about the necklace taht day.

Of course she did it.

I've seen reviews that we deserved to see "how" she did it, but I like keeping the ending vague, and it still does makes you wonder if she really did it! (she did).

I like how the red herrings (The black guy and Tate) are suspects during the movie, and remain (possible) suspects as the credits roll, since the actual murder was not shown. But when you give it some more thought, or view the ending a 2nd time, the combination of the poem and the necklace really do confirm that she was the murderer. And if you're still not convinced, go read the book!