How to get your friend to stop from telling the teacher?

Ok so my friends wrote me a threat note and it was completely harmless. Then we switched and I accidentally left it in the desk so the next class comes and a girl with the same name as me finds it and bring it to the principal. Well now the principal is trying to find out who did it and the person that did let's say her name Is cloe. Well if cloe gets in trouble again she will get expelled. This other girl let's say her name is bre. She no's and now is trying to tell the principal. How do we stop her