destroying toys and dolls

My daughter is 13 years old but developmentally delayed and has bipolar disorder. Also diagnosed with Reactive Attachment Disorder. (she was adopted at age 3, just to give you some background that might be relevant to my question) She has started destroying her stuffed animals. I find her cutting their limbs off, heads off, etc,, She cut the head of a baby doll open as well.  And tonight I found a knife in her bed under the covers!? What is going on!???  

[margypops]

Has something happened recently may have upset her, new school, home,anything happen with family .I am assuming you asked her why she is doing it, did she have a reason ?