Divorce Support Forums: Is it legal for Ex to withold medical card info?

My husband's EX is refusing to give us the medical insurance information for their 2 children so that we can go to family counseling. She has tried to drive a wedge between the children and us since the day I met my husband. She says since she is the one that pays for the insurance, we have no right to use it for the kids since this is 'OUR' problem. She has never had the best interest for her children in mind and uses them as manipulating tools. How sad! Legally, it seems that she is denying her children medical attention by denying use of the insurance. Am I correct? I am sure if one of the children fell here and broke and arm, she would want them attended to. Family counseling/mental issues should be no different. We told her we'd pay the copay and anything that insurance would not pick up. It's a control issue to her though. Doesn't she HAVE to provide us with the information? The child support we pay is computed taking into consideration that she pays for their insurance, so the support she receives from us helps to cover this insurance.Your input is appreciated.