My dog who sleeps with me, woke me at 3am barking like crazy...?

I have a small dog who sleeps on my bed. This night at 3pm i was woken by my dog barking loudly staring at the doorway. I assumed her barking because she could hear my daughter walking up the hallway to come and sleep with us. So i turned my head to look at the doorway expecting to see my sleepy daughter only to my shock saw very clearly a very tall white ghost of a very old lady, the image was looking at the dog barking madly and seemed to be moving its head around in a very confused manner,i could also feel the energy and it was quite bright also. There was no anger, or ill will felt from the ghost but i was petrified just the same. In absolute fear and shock i turned my head to face the other way and could see it in the mirror, with the dog still barking i watched in a fear i have never experienced before, thinking how do i get it to go away, i then shook my doona and yelled out to my daughter, and it faded away. I lay there a while till i had the courage to turn on lights and check on my daughter who was sound asleep. i have lived in this unit 5 years and have never had anything like this happen before, i am now very fearful and am wondering why it came to me. My intuition tells me it was lost or confused and was not there for me! It did not feel familiar, nor did it feel to have any message or omen. So what would have made it visible to me and my dog? I am filled with questions that cannot be answered and am totally freaked out! Would appreciate any views you may have.. Regards Jo C....