What if she travels outside of Canada?

Canada's border officials are VERY cautious about abductions. Believe me! I am a single parent, and I was travelling with my daughter in the USA (with permission from her mother). Just as we were to return to Canada, she got into a bit of trouble. About an hour later, at the border, the people there detected a problem - just by looking at her, and hauled us in, separated us, and interviewed us both separately. I produced the permission letter, and they contacted my ex. Now, everything was fine, and in order, but it sure showed me the care these people take. It was an inconvenience for me, for sure, but if that's how they act for returning citizens with permission from the other parent, my guess is that they would call in the RCMP pretty quickly for a case like what you suggest. They did a great job of checking things out, in my opinion. They are very aware of abductions - there were posters, and pictures of missing kids all over the place in the building.