Was my Nana possessed?

I believe that my late Nana was once possessed. I don't remember much of her because she passed when I was about 8 however I will never forget one incident. <br><br>I had a sleepover with my cousins at their house and we must have been bored so we played oujia board. It was fun asking questions we were a little spooked out as well. Suddenly I get a tap on my window and I see my Nana with a weird grin on her face looking through the window. I scream as my cousins ask me what wrong. I show them and they scream as well. They run and call my uncle. We rush to the window and there is no one. My uncle went outside only to find no one. <br><br>Was it my Nanas spirit trying to tell us something or the work of a demon. I will never forget that weird look on her face.