Anna, you always want a hard explosive initial consonant for a dog's name so you instantly get their attention when you want it - so of your choices Pearl, Dagna, Calista and Dougie would work best - Calista will probably end up Callie or Cal ;-) and the hard 'K' is your best choice with Pearl second. 'D' is lingua-alveolar and doesn't have the same punch.
This is a smart dog, but also independent minded as a herder with a job to do, so you're going to want her to stop and look when you call her...try the names and see when she perks her ears...
They look beautiful out there
