19.
If Manaphy is a prince then I would guess that Phione is one too. In our world royal status varies depending on the country and time period, but in many instances the child of the crown prince is called a prince or a princess as well. In the Japanese royal family Fumihito, Crown Prince Akishino has a son who is a prince, that would be Prince Hisahito. He has two daughters also, one is Princess Mako. The other's name is Kako. Technically Kako is no longer a princess, but that's because she fell in love with a commoner and gave up her title to be with him in a modern day love story.