My Daughter Is 15 Years Old. She Was Studying Last

My daughter is 15 years old. She was studying last night and I walked in the room. She was waving her right arm in the air and looked very out of it. I asked her if she was ok and she started to speak and slurred her words. She repeated it again, which took some effort. I asked her what was wrong and she said she felt like she was dreaming or out of it. And she proceeded to tell me about her numb arm. After further discussion she said this has happened to her other times. Any ideas of what might cause this? I scheduled an appointment with her Pediatrician tomorrow morning.