13-Year-Old daughter got another kid in school in trouble for something she did.

We've never had any big issues with our daughter, but as well as intelligent she's rather scatter-brained and impulsive. This past week we've noticed she seemed to be really depressed, just sitting around the house rather than watching TV, no interest in going outside, eating very little. Our attempts to ask her what the problem is have been rebuffed. But she told her 15 year old sister who told us.Her pre-algebra class has a rule that you get a detention for not coming to class prepared, and she had left her book at home that day. One of her classmates had left her bag laying around, so our daughter grabbed the classmates book. So of course it was the classmate that got the detention, and she was really, really upset, claiming that she had never been in trouble before and her parents were going to be so angry at her and she was going to be in so much trouble at home.I guess the thought never occurred to the teacher to check to make sure everyone had their assigned book and probably figured the classmate had just forgotten it and was lying about someone taking it to get out of trouble. After class our daughter dumped the book off at lost and found so the classmate did get it back and didn't have to pay for it.Out daughter made a comment to her sister to the effect that we would never forgive her we found out what she did; she's convinced she's an evil person, is basically trying to ground herself. We're kind of at a loss how to approach this situation now so we'd appreciate any advice. Thanks. via /r/Parenting http://ift.tt/2xJ25d0