Your daughter was not incompetent to teach French, but she was not certified to teach in Ontario, as teaching falls under provincial jurisdiction. We train excellent teachers, but accreditation is given by the Department of Education of Quebec. In my humble opinion, there should be specific agreements that apply to language teachers. If there isn't any specific agreement, Ontario cannot recognize teachers who were trained in Quebec. Similarly, Quebec does not recognize teachers trained in British Columbia, etc.
The situation is different and varies from one province to the next in terms of sciences; but as regards languages, I think we would all be doing one another a favour if we were to agree... I know that there are certain agreements, but those agreements must be specific agreements between provincial departments of education.