Congratulations!!! So exciting!
A lot of times breeders like to keep a theme in the registered names. All "D" pups or only dogs named after mountains, or all "magic" theme. If you don't want to name her a "D" name, you can always have her registered name be whatever the breeder wants and have her call name (what you call her) be whatever you want!
rory's registered name has no relation to his call name.