My feeling is that she is upset about something and is acting out, so check on what has been happening her life could make her unhappy , could be she is seeking attention, negative attention is better than none. Does hse say whyy she takes these things? is school going well , any new Family ,any new happenings could make her feel insecure.
Sounds like she is hanging out with a bad influence. How was your relationship before this stuff started? When I was that age I started to hang out with a girl who had a lot of issues. She stole from her mom, and I thought she was cool so I did it a couple times. Luckily I became friends with another girl, who was a much better influence. Check on her friends, maybe she is being influenced. By the way that bad friend also introduced me to drugs, so be aware.