The police here are reluctant to bring charges since the victim is an unreliable witness. We are left to seek redress in civil court. You are across state lines and over an international border, so I cannot tell you whether criminal prosecution might succeed in Quebec. However, I can offer a practical suggestion that applies whether you are in Canada or in Texas.
Governments maintain bureaus to investigate and to remedy elder abuse and exploitation.
Texas has declared that May is Elder Abuse Prevention Month. DPRS can be called when you need to report a suspicious situation. This can be something a caretaker consciously allows, or that happens because a frail elderly person can no longer provide self-care. It sounds like your mother has suffered exploitation, at least as it is defined by Texas law. In 1999, DPRS completed 54,478 investigations of neglect, abuse or exploitation of the elderly.