Can she claim wrong venue or our previous state still has jurisdiction over the case since there is no other court involved?

A final parental agreement was entered and since then, the mother and child left per the agreement. I also left and moved. However, the mother didn’t transfer the case to where she is. She has been in contempt of the court order in the parental plan and I filed a motion of contempt against her. She is refusing to take back the child to live with her per the agreement and the child has been with me the last 6 months. She has also been receiving child support the entire 6 months the child has been here and I have been paying all the child's expense. I have asked also the court in the contempt for retro pay of child support. Would the court order her to pay back that child support?