Our live-in niece, who is almost like our daughter, is named Calista. She's 10, and I don't think we've met another Calista. I love her name. I think it's very pretty and feminine, easy to spell/pronounce, traditional but not overused. She doesn't have a nickname; we call her by her name. Go for it!
It's a very nice name. I've never met one in real life. I like the NN possibility of Callie if you wanted to use one.