AliCat...hubby absolutely needs to get the medical done for his daughter. He needs to mend some fences, whatever it takes, and have her do the medical. CIC is very strict lately about parents not getting medicals done for children to whom they have reasonable access.
I have seen cases where they basically told the parent, "if you don't get the medical done, you don't get a visa", because the parent had visitation rights as per the court. One father had to travel far away from where he lived, go and bring the police with him to try and see the child, and when the mother refused he had to get the police to write a report for him to take to court for the judge to order the mother to produce the child so he could have his court-ordered visitation. CIC were not prepared to give him a visa until they saw all that paperwork!
If his ex protests, he needs to explain to her that their daughter doing the medical protects his right to sponsor her in future if, God forbid, something bad happens to her. It also gives their daughter additional opportunities in life, and opportunities should never be squandered in a fit of spitefulness or anger.
As for the daughter, if she protests and she's under 18, she needs to do as her father says. I don't hold with children dictating to adults what they will and will not do, and then turn around and expect these same adults to support them and finance their lives. When she turns 18 and is a legal adult, she is free to tell him to go about his business if she doesn't want to have anything to do with him, until then, he is the parent, and she is a minor child and he has legal rights.
If she is over 18, he cannot compel her, but she should be fully made to understand that if she does not do the medical, and anything happens to her mother, God forbid, she is on her own because he will NEVER be able to sponsor her again. And I do mean NEVER.
This is a serious matter, and I hope he can have it sorted. Good luck!