Why "D"?

Some of you may wonder why I mentioned we wanted to name her Kara, but then I started referring to her as "D". Her Chinese name is Da Xin and because she will most likely be 11 by the time she comes home, we want to give her the option of whether or not she wants an American name. We are hoping she says yes, in which case we will name her Kara Da Xin. However, if she says no, then we will call her by her Chinese name. Unfortunately, we know that if she decides to keep it, most people will not pronounce it correctly. It is a choose we want to give her, though. So for now... I'm not sure what to call her, so I'm calling her "D". :)