Little sister causing severe family dysfunction. What to do?

Adoption? jk, keep in mind that she is 12, going through changes she doesnt fully understand. i would have her keep up with the psychologist, it sometimes takes years to get to the root problem. most of all stay patient, remember that she is a child and any ill feelings towards her wont help the situation. it sounds like a very distressing situation and it is possible that she has some sort of chemical imbalance. its also possible that some event happened that made her start to act this way such as a ual ault or other traumatic situation. i wish you the best of luck. keep giving her love no mater what and hope it gets better. it may be a defense mechanism of some sort,