Can the police request to see completion of a rehab program down the road and file charges if she doesn't have a certificate?

My daughter was in a car with a kid who was selling drugs and was taken to the local police station. When my husband and I went to pick her up, we were told she can choose to go to rehab or a warrant will be issued for her arrest. She started going to rehab as an outpatient, but it's overwhelming and she skipped today. The fellow selling the drugs is in jail. Two others that were in the car with my daughter were given the same choice and did not do anything. My daughter who is 18 says the cops didn't file charges and she's not going to rehab anymore. Is she correct? She did not have any drugs on her when this arrest occurred. I am guessing that's why the police gave her this option.