Good question! Legally speaking, this is a grey area. As the employee is not your visa, is can fall on either party to insure her medically. That being said, if she is working with you (has a labour card) and is not insured, there is a high possibility the company will be fined, potentially as well as the father. As it's a major prerequisite that all companies ensure their employees, leaving her without medical insurance is a risk for your company and you might get pegged with fines.
If you're struggling to find a plan for this particular candidate, why not check out Bayzat? We use it for our company to get all our insurance policies since it gives you different options and allows you to compare between plans.