She keeps stealing from me

my 12 year old keeps stealing from me - she uses my credit card without permission and lies about it. She has been punished severely already, but I don't know how to get her to stop it!
 We are up over $1,000 now, mostly for i-tunes. Short of having her arrested, I have no idea how to make this nightmare stop. She is now grounded (again) and has no access to the i-pod or computer or tv, her favorite things, and still it has happened again.
So, how, she has lost the i-pod permanently. But the school has issued her a laptop, which she can take home.
I'm so depressed I can't stand it!