Wife has vision

I really wasn't sure how to title this one. I think there is a good chance that my wife experienced a waking dream; however, she is firmly convienced she did not. Last night, well after we turned in, I was aroused by by wife shouting out. Thinking she had a dream, I went rapidly back to sleep. This morning she asked if I heard her shout out last night. I said I had but assumed it was in her sleep. She insisted she was awake at the time. She said she was awakened by the older dogs low growls. She couldn't figure what he was disturbed about so she aroused to see if she could hear anything that might have set him going. When she looked up from the bed she saw a white misty form standing beside the bed and thats when she shouted. She said the misty form vanished with her shout and and the dog stopped growling. So, I was awakened by the shout, but being half asleep I saw nothing but went back to sleep. Our older dog must have been aware of something to be making warning growls....but what? Was it a waking dream, or did she experience something paranormal???? Our younger dog could sleep through a train wreck, so shes no help here.