She will find a job but not necessarily in her field or skilled. If she doesn’t speak French then most customer service jobs will be out. Do a quick job search as most skilled jobs will require French and English.
My two cents is that it's certainly possible but will be difficult to secure a banking job in Montreal without French. Some of this may also depend exactly what her banking experience is. IMO she should be prepared to work in a different occupation (potentially not skilled or semi-skilled). I would focus on trying to find banking jobs that are remote work vs. banking jobs located in Quebec (the Quebec ones generally require French). There aren't a ton of fully remote jobs with the big banks. Although many are WFH right now, there's an expectation that people be able to work at least a few days in the office once things return back to semi-normal.
