This picks up immediately after Dragonheart. It lasts five months and things get worse and worse as more and more dragons die. The dragongirl is Fiona who we met when she was two in Dragon Harper by both mother and son. In this book she's either twelve or fourteen, depending on how you look at it.
She's grown up to be a queen rider, a person who fixes everything, who is always happy, and initiates polyamory.
This book ends with a great event, but it's not the end of the story.