I would lecture the girl, let her know that you don't approve of her shoplifting and that she better not involved your daughter in it. Let her know point blank this is a warning. I would tell this little girl too, that you are going to give her picture to every store around there and let them know she shoplifts and be careful if she walks into their store. I guarantee she'll change her behavior. If she doesn't then she will not hang out with your daughter.
I found out that my daughter was buying things for some of her friends, taking them places (having us take them places) then I had a long talk with her. Do you want to be used or be someone's doormat? I told her how valuable she is that she needs to see her own self worth. Of course she didn't want to be left out, but she finally saw how she was being used. I told her I would not be used by her friends and neither should she. They were not real friends. If you have to buy friendship, find a real friend...
Tell your daughter how important it is to be a good friend. Remind her friendship isn't based off of how much you can buy someone else. Remind her of her self worth, and don't let anyone make her out to be something less.
At 12 you still have control over her. I would limit the time she spends with this girl until the girl can restore some trust in you.