In Quest of the Hart, the necklace is given to Princess Kaylee by Navon, the hart, to carry a drop of dragon's blood needed to end the spell on Prince Devlin.
In Different Kind if Knight, Princess Rielle collects bits of the creatures she has killed and wears them wears them on a trophy necklace.
What you might not know it that the necklace on the cover of Charmed Memories is one I made several years ago while playing around with jewelry making. In fact, here's a picture I sent to Marion Sipe (the cover artist) to use:
For Christmas I needed a gift for my niece (who happens to be my biggest fan.) So, I decided I'd create at the necklaces from the first two books for her (I hadn't seen the necklace Ck Volnek created for book 3 at this time). And this is how they turned out:
After seeing them, my mother-in-law knew she had to have one, so for Mother's Day, I made a (similar) heart necklace for her and my own mother, as well as this:
As you can see, the stones and wire wrapping are all slightly different, but i think they each capture the heart of the necklace well. What do you think?