Do you have to pay child support if your daughter had a child and left home at 16 and is not going to school in Alabama?

You will need to obtain clearance from the courts to end child support. Otherwise, you risk running into arrears. Seek legal representation.

If she is living on her own, and I'm assuming with her legal guardians consent since she is not allowed to move out otherwise, you can see to that it is paid directly to her. She is not emancipated just because she had a child and moved out so therefor you are obligated to support her until she is 18 or emancipated. The chance the court will allow you to end it is not big.