This is Dolphin the SeaWing. Dolphin was best friends with Orca before she went evil, and Dolphin was the only one who knew about Orca's magic. Dolphin knew about only two things that Orca had enchanted, although she assumed there were more. One was Orca's pet frog named Amica- that Orca had carved from green seaglass. (Orca told Dolphin she had gotten the idea from a story about an ancient SeaWing.) The other was Dolphin's bracelet- A shard of pink coral threaded on silver wire. It was enchanted to keep Dolphin safe. ("So no one can hurt you." Orca had said. Dolphin remembered her muttering; "Not even my mother.") Unfortunately it wasn't a very specific enchantment, so Dolphin could be hurt and could die, just couldn't be killed.
Dolphin was planning to talk to her friend because she started seeming off- but Dolphin didn't get the chance because she was seeing the princess less and less. Then Dolphin was summoned by the Queen and was told Dolphin's family was being moved so they could be helpful elsewhere. Dolphin was very sad and went and said goodbye to her best friend. Orca was not herself, and told Dolphin the real reason her family was being moved- Coral didn't want Orca spending so much time with a 'commoner'. Orca was getting very mad and said she would kill Coral for this. Dolphin tried to stop her but Orca lashed out with her magic, and thought she killed Dolphin. That was the final straw for her, and Orca went and challenged the queen.
Of course, Dolphin didn't die although she came very close. She took Amica and fled, and ended up in Possibly, where she made a new life for herself.