Chatterbox: Down to Earth

So this is sort of an S.I... I am going to be a charrie from a book and you have to guess who the charrie is and what book he/she is from.

Hello.

My name is... well, I'm not supposed to tell you my name. But anyways. I have a best friend named Claire, and she and I met under difficult curcumstances. We were both at a finishing school, learning how to be 'proper ladies', but I hated it there! All my life, I'd wanted to be a pirate. I can tread water for 37 minutes. I can tie any knot faster than a fleet of sailors, and I owned a rather pointy sword. But my father, who is an admiral, just told me to stop playing such games, patted my head, and told me to 'run along and be a good little girl.' So I decided to run away from finishing school to become a pirate under a man named Jasper Fletcher, terror of the high seas. But I can't tell you the rest, because it would give away the book!
Who am I?

BTW, this is the easiest level of guessing. I will be posting harder ones.