Can my step daughter's mother be held in contempt by not enforcing the custody agreement set in place?

My husband has not seen his 13 year old daughter since January. He attends all her sporting events, calls, texts her everyday but she will not return his calls, see him or respond to him in any way. We know her mother is alienating the child and basically brainswashing her to feel she does not need a father or a man in her life. The daughter cuts ties with her all her paternal relatives, won't return calls or texts from her paternal grandparents or aunt. The mother is withholding imperative medical information regarding the daughter from my husband, like the fact that the duaghter had cancerous moles removed from her body..only found out when the mom wanted money to pay the bill. The daughter is afraid of the mother. I just wish there was something we could do. My husband basically raised his daughter by himself until she was 9. Now he has no contact with her what so ever. It is breaking him down. Should a law guardian be involved or does that require returning to court?