My 13 year old sister recently has been talking and laughing alot to herself. Me and my family is trying to figure out what is causing her to do this. She would start talking to somone who's not there and giving them a name to refer to. I'm really trying to find out what's causing her to be like this. from time to time she would like to stay in her room and hates being together with the rest of the family, she rather be by herself. please can someone help me thanks