The Shadow Girl

This happened to me a couple of years ago while I was still in middle school. My sister the one I will be mentioning in the story was currently still in high school. When me and my family moved into our new house I had to share a room with my middle sister because the house only had three rooms and my oldest sister wanted a room to herself so me and my middle sister ended up sharing a room. There were two beds in the room both against the wall. One night around 11pm I was laying in my bed trying to fall asleep while my sister was having a conversation with one of her friends over the phone. I remember her sitting on her bed with her back against the wall and I was laying down facing my sister. I couldn't really fall asleep so I just laid there with my eyes open hoping sooner or later my eyes would get tired and I would be able to fall asleep. A couple minutes passed and I was still awake and my sister was still on the phone. But then something moved next to her which caught my attention. I looked at it carefully trying to make sure I wasn't seeing things. I looked again. It was a shadow of a girl right beside my sister but she hadn't noticed it until I got up and whispered her name while pointing at the shadow. She told her friend over the phone holdup my sisters trying to tell me something and when she looked to her right she screamed, dropped her phone and stormed out of the room. Her reaction frightened me even more so I ran behind her. I remember we woke up everyone in the house but of course when everyone went to go check what the fuss was about the shadow was no longer there. No one really believed us and joked about how me and my sister had gone crazy. But me and my sister both know what we saw. It's been years now but I would be lying if I said we kept seeing shadows but no that was it.