time to get real

     At what point do you say enough is enough?  My soon-to-be 18 year old is just a mean old bully.  She is very hurtful in the things that she says and does and it is affecting everyone in the family, except my husband, who has built an emotional wall against her.  I can't do that.  I love her, and her venomous words and actions are tearing me apart.  She keeps threatening to move- and at this point I wish she would.  That is awful, but there it is.  She is ripping this family to shreds.  She torments the other kids, and my 9 yo son feels it terribly.  He has become depressed and if afraid of her.  I can't blame him, I am too.  She won't take her bipolar meds...or any other meds...and she is seriously out of control.  I don't know what to do.  I am fed up, torn up, and out of ideas.