I have always loved the name Deidra. It's beautiful and unique. I think it's so much prettier then Deirdra. Or Deirdre. I also love the nickname Deedee.
I once knew a Deidra, she went by Dee though. For the longest time I didn't know what Dee was short for, and didn't realize it was for such a unique, pretty name. I prefer Deirdre, though, because I like that middle 'r'.