Window Dust Ghost Picture

Recently, we received this very cool ghost picture of dust forming on a window and into a face. Is it a ghost in the picture? Did grandmother cause it to appear as some sign? You decide:

"My name is Marcee Bain and I live in Corvallis, MT. About a month after my Grandma passed away, I noticed a weird dust on the upper right corner of my window in my new house. I walked over to investigate and swiped the bottom right side with my finger, as you can see in the picture. It was a thick dust, but what surprised me more was that I could see a distinct face in the middle of it. I showed it to my family members and they all agreed it was weird. I kept it there for three weeks and took some pictures of it with my digital camera, with a flash. In the pictures, even more of the dust showed up and upon further examination, I could see several other faces. I have no idea what it was, but it has yet to return."