The Silver Horse by Kate Forsyth
Ages ago I was asked to read this series because a parent expressed concern that some of the themes in the series were far too controversial for young readers. So far I have managed to find the time to read the first two books in the series and in my opinion these two are fine.
Last August I reviewed the first book in the series, the Gypsy Crown. You will need to have read the first book, or at least a comprehensive review of the book in order for the plot of this second book to make sense. In the second book the children are negotiating for the second charm, held by a family of horse traders. Emilia must sacrifice her beloved horse to get this charm, but her confidence that the magic will succeed convinces her that it is only a matter of time before the charm can be returned and her horse reclaimed.
Again this is very much a transition book. It tells its own story, but needs to be read in the context of the full series.