Have a serious talk with you friend, and let her know that you're not going to steal things anymore and that you're not going to the mall with her anymore if she's going to shoplift. Then have the integrity to stand by your word.

The man of integrity walks securely, but he who takes crooked paths will be found out. (Proverbs 10:9)

"So then, King Agrippa, I was not disobedient to the vision from heaven. First to those in Damascus, then to those in Jerusalem and in all Judea, and to the Gentiles also, I preached that they should repent and turn to God and prove their repentance by their deeds." (Acts 26:19-20)

Repent, then, and turn to God, so that your sins may be wiped out, that times of refreshing may come from the Lord. (Act 3:19)

We need to prove our repentance by our deeds.