You do not state how old your child is? As there would be diferent answers that would be relative to the issue if I knew how old she was. Would you be so kind as to post her age please.
Kid Angel Foundation
Set a timer. She must sit there and work on her homework until the timer goes off.
You also need to sit with her. She needs to stay on task and be correcting the work as she goes along. If she writes a sentence without a capital letter, fix right away. If she doesn't do a math problem correctly, fix it right away. When the timer goes off, let her go and play for a certain amount of time, but she should come back to the table for another "work period" to continue what she did not finish the first time.
Firmness and consistency is needed. You'll be glad you stuck with it.