What do You think about Heather The Violet Fairy (2006)?
This book worked well as a satisfying conclusion for the series. It was fun seeing all the fairies again, all together! I like how even though these stories are formulaic - in each book, the girls find a fairy while goblins try to stop them - there is still a respectable amount of variety to make each story unique. In this one, when the girls find Heather the Violet Fairy, goblins are nowhere to be seen. It's not until all seven fairies are reunited that Jack Frost himself causes trouble. Surprisingly, this book provides some background on Jack Frost, which is interesting if you've ever wondered why he has a place in Fairyland at all. We even see a bit of a soft spot in him!
—Irene