Help getting insurance for my niece

My 16 year old niece has come to live with my wife and I in Illinois. It's not a formal adoption (her mom has okayed this with the knowledge of Child Protective Services in her state of North Carolina. The documentation from her mother and from North Carolina Children's services was enough to get her in school here, but it doesn't seem that's true of my insurance. To get her on my insurance she'd need to be adopted formally or I'd need to have a Qualified Medical Support Order.

Anyone have any idea how possible it would be to get something like a Qualified Medical Support Order designating me as being responsible for her health care coverage?

If not I might look into state aid of some type. She's living with us, but her mom still technically has custody. When I spoke with North Carolina Medicaid (what she HAD been on) they indicated she couldn't stay on that (since she was enrolled in high school in Illinois) but that Illinois might based on her MOTHER'S income (not mine, it wouldn't qualify).

In addition it does appear in the child support settlement for her dad (my brother) HE was actually obligated to take care of that. So then it might be HIS eligibility to get her on state aid.

Just trying to find the best way to get her on insurance. Right now she's too much with us for the State of North Carolina to cover her, but not enough for my insurance to cover her. How do I bridge this gap?