Granted, I've only known two, and both were deer-dra. Not certain on their spellings though. I do prefer
Deirdre to Deirdra by far. Deirdra just seems kind of dumbed down to me, and I really don't think deer-dree makes sense from the original spelling anyway.
I've loved this name since meeting one who was about 4 years old. It was at a
Ren Fest and she was all dressed up in a little garb gown, red velvet, with an embroidered cap thing on. Long, long brown hair. She looked up at me and said in such an adult manner, "Hi, my name is
Deirdre." It was just so charming.