I read the first two books a few years ago so details are hazy. I remember it was probably a young adult fiction series. It was a trilogy and the last book came out this year (2014). There was a princess in it and she had a dragon. The people in the palace knew (from what I think I recall) but she had to keep it a secret from the rest of the land as people were very scared of dragons. There was a servant boy in it too and I have a feeling his name started with C. I could be wrong though. I also think the name of the first book started with S but I can't remember for sure. I'm also pretty sure that in the second book, the princess and the servant boy fell in love. I remember something about a forest and the princess loving to ride her dragon and flying over it. I really can't remember much more except that there was a war in the second book (I think) and it related to the dragon as some people from outside the palace walls found out about the dragon. The dragon was obviously friendly, but as I recall, everyone in the palace wanted the dragon to go into hiding but the princess decided to fight in the war. I can't remember the outcome. The author of the series was a female.
The Trelian Series by Michelle Knudsen, maybe. The last book came out in 2016. There is an apprentice named Calen; the princess is named Meglynne.
From the second book, The Princess of Trelian:
"She couldn't stop flying with Jakl altogether. But maybe she could make sure they flew out over the forest, where they wouldn't be seen"
"You're going to let my dragon openly fight for Trelian?"
The dragon is a secret. There is a war. The third book was released April 2016.