Is it forbidden for a father to use his private health insurance to purchase medication for his daughter's bladder infection—medication that is expensive in Canada and cheaper in the Gulf—?

Your father's circumvention of the insurance to buy medicine for you in his name is not permissible. If the insurance is commercial and forbidden, it is not permissible to voluntarily subscribe to it. If the father has subscribed to it, he is not allowed to benefit from it more than what he subscribed with. It is permissible to resort to stratagem to extract one's right if the price of the medicine is equal to or less than the insurance premium.