Air Canada has to decide whether to carry her, but Mexico does allow her in without a passport. She needs a proper birth certificate as well as government issued photo ID.
http://www.inami.gob.mx/EN/index.php?page/not_need_visa
Under an agreement with Canada and the USA, those countries' citizens may prove their nationality with a passport or other public documents, such as:
Certified copy of birth certificate.
Voter registration card.
Naturalization certificate.
If any of these documents lack a photograph, travelers must prove their nationality with another official identification: