Okay, first of all, if she is taking the things and not owning up to it, you need to make her take responsibility for it. If there aren't any consequences, she won't see a reason to stop.
My cousin did this when he was small. He would take match box cars and other small toys. What set him straight (he's now in his early twenties) was his Dad making him take each and every toy back to its rightful owner and apologize. Afterwards he was grounded for about 2 weeks as well.
At this age, I don't think it would be a stigma that follows her for the rest of her life. A few weeks of embarrassment over the situation on her part could be the deterrent that keeps her from shoplifting later and the possible consequences that can go with it. Also, it won't be very long before one of her friends or classmates does something that causes the attention to shift to them.
I wish you luck with the situation.