Not entirely clear to me. Did she drive to YYZ to find out she had been offloaded from the YYZ-CDG leg?

THat would not be quite the agent's doing. Standard policy: if you don't make the first leg, you get offloaded from the second one. They had no idea she would make her way to YYZ. Perhaps she should have asked the agent to make sure the second leg would not be canceled, and that she was on her way. Nut then thhis was probably a contract gent who might not be terribly familiar with the AC proveedures.