Tricare coverage for dependent.

Hello, I have a question about Tricare Health Insurance for a dependent. The question is about my niece. Her father is in the navy, and my niece was on his Tricare plan. She is now no longer on her father’s plan. But, she is trying to get medicaid trough socail services now. She was approved for Medicaid, but, Medicaid needs a letter from Tricare saying that she is no longer on the plan before they can cover her. So my question is where would she get the letter? And what should the letter say?