Is my sister mentally unbalanced? If so, what is it?

Ok, so my sister is just plain MENTAL to me. Some things she does are : She talks to herself. She laughs idiotically at everything (sometimes and most times, they aren't even funny). She laughs at her own jokes. She talks to inanimate objects for instance, one time I heard her yelling at the radio, because she turned it to the Spanish channel -.- She does weird hand motions randomly. She blurts out random words out of nowhere. She's really mean, likes to push me out of the way to do her own stuff. She gets straight A's, and talks about weird smarty stuff all the time. She likes to show off what she learned by telling everybody. She talks SO LOUD on the phone, and always put her friends on speakerphone. at night. when im sleeping. And she has this CRAZY mental-like idiot laugh. Is she mentally unbalanced, and if so what's this disease she has?